Methods of investigation in hematology

Methods of investigation in hematology.

Anemia.

 

 

Normal Blood and Marrow

Blood is composed of plasma and cells suspended in plasma. The plasma is largely made up of water in which many chemicals are dissolved. These chemicals include:

• Proteins (such as albumin),

• Hormones (such as thyroid hormone),

• Minerals (such as iron),

• Vitamins (such as folic acid), and

• Antibodies, including those we develop from our vaccinations (such as poliovirus antibodies).

The cells suspended in plasma include red cells, platelets and white cells (neutrophils, eosinophils, basophils, monocytes and lymphocytes).

• The red cells make up half the volume of the blood. They are filled with hemoglobin, the protein that picks up oxygen in the lungs and delivers oxygen to the cells all around the body.

• The platelets are small cells (one-tenth the size of red cells) that help stop bleeding at the site of an injury in the body. For example, when an individual has a cut, the vessels that carry blood are torn open. Platelets stick to the torn surface of the vessel, clump together and plug up the bleeding site. Later, a firm clot forms. The vessel wall then heals at the site of the clot and returns to its normal state.

• The neutrophils and monocytes are white cells. They are called phagocytes (or eating cells) because they can ingest bacteria or fungi and kill them. Unlike the red cells and platelets, the white cells leave the blood and enter the tissues, where they can ingest invading bacteria or fungi and help combat infection. Eosinophils and basophils are two additional types of white cells that respond to allergens.

• Most lymphocytes, another type of white cell, are in the lymph nodes, the spleen, and lymphatic channels, but some enter the blood. There are three major types of lymphocytes: T cells, B cells and natural killer cells. These cells are a key part of the immune system.

 

 

 

 

Marrow is a spongy tissue where blood cell development takes place. It occupies the central cavity of bones. In newborns, all bones have active marrow. By the time a person reaches young adulthood, the bones of the hands, feet, arms, and legs no longer have functioning marrow. The backbones (vertebrae), hip and shoulder bones, ribs, breastbone, and skull contain marrow that makes blood cells in adults. Blood passes through the marrow and picks up formed red and white cells, and platelets, for circulation.

 

 

Figure 2. This figure depicts an abbreviated diagram of the process of hematopoiesis. This process involves the development of functional blood and lymphatic cells from stem cells.

 

Pict. 1 The scheme of blood cells

When the fully developed and functional cells are formed, they leave the marrow and enter the blood. In healthy individuals there are enough stem cells to keep producing new blood cells continuously.

Some stem cells enter the blood and circulate. They are present in such small numbers that they cannot be counted or identified in the usual type of blood counts. Their presence in the blood is important because they can be collected by a special technique and can be transplanted into a recipient if enough stem cells are harvested from a compatible donor.

Stem cell circulation, from marrow to blood and back, also occurs in the fetus. After birth, placental and umbilical cord blood can be collected, stored and used as a source of stem cells for transplantation.

In summary, blood cells are made in the marrow. When the cells are formed and functional, they leave the marrow and enter the blood. The red cells and the platelets carry out their respective functions of delivering oxygen and plugging up injured blood vessels throughout the body. The white cells (neutrophils, eosinophils, basophils, monocytes and lymphocytes) enter the tissues (for example, the lungs) to combat infections, such as pneumonia, and perform other immune functions.

 

 

Pict. 2  Human blood smear: a - erythrocytes; b - neutrophil; c - eosinophil; d - lymphocyte.

 

 

Pict. 3. A scanning electron microscope (SEM) image of normal circulating human blood.

 One can see red blood cells, several knobby white blood cells including lymphocytes, a monocyte, a neutrophil, and many small disc-shaped platelets.

 

 

 

 

 

Pict. 4. From left to right: erythrocyte, thrombocyte, leukocyte.

 

 

 

Pict. 5 Blood is the only fluid tissue in the body. Blood transports oxygen and nutrients to body tissues, and returns waste and carbon dioxide. Blood distributes nearly everything that is carried from one area in the body to another place within the body. For instance, hormones are transported from the endocrine organs to their target organs. Blood helps maintain body temperature and normal pH levels in body tissues. The protective functions of blood include clot formation and the prevention of infection.

 

 

The Lymphatic System

The lymphatic system and the blood cell-forming system in the marrow are closely related. Most lymphocytes are in the lymph nodes and other parts of the lymphatic system such as the skin, spleen, tonsils and adenoids (special lymph nodes), intestinal lining, and in young people, the thymus. The lymphocytes circulate through channels called lymphatics that connect the lymph nodes scattered throughout the body. The lymphatic channels collect into large ducts that empty into a blood vessel. The lymphocytes enter the blood via these ducts. There are three types of lymphocytes. T lymphocytes (T cells) originate in the thymus, hence the designation "T." The B lymphocytes (B cells) originate in the marrow in bone. (The "B" comes from the word "bursa," an organ in birds that was first found to be the source of B lymphocytes.) B lymphocytes make antibodies in response to foreign antigens, especially microbes. Collections of B lymphocytes are present in the marrow, which is an important site for their function.

The T lymphocytes have several functions, including assisting B lymphocytes to make antibodies against invading bacteria, viruses, or other microbes. The antibodies attach to the microbe and in so doing make it possible for other white cells to ingest and kill them. The white cells recognizes the antibody and pull (ingest) it into the cell with its attached microbe. The cells can then kill and digest the microbes.

The third type of lymphocyte, natural killer or NK cells, attack virus-infected cells as a natural function without requiring antibody or other mediation. T cells and NK cells have other functions as well, and are important elements in studies that are designing immunotherapies to treat leukemia and other cancers.

 

Topographia organs of hematopoiesis and lymphatic system

 

HEMATOPOIESIS AND THE PHYSIOLOGIC BASIS OF RED CELL PRODUCTION

Hematopoiesis is the process by which the formed elements of the blood are produced. The process is regulated through a series of steps beginning with the pluripotent hematopoietic stem cell. Stem cells are capable of producing red cells, all classes of granulocytes, monocytes, platelets, and the cells of the immune system. Commitment of the stem cell to the specific cell lineages appears not to be regulated by known exogenous growth factors or cytokines. Rather, stem cells develop into differentiated cell types through incompletely defined molecular events that are intrinsic to the stem cell itself (Chap. 104). Following lineage commitment (or differentiation), hematopoietic progenitor and precursor cells come increasingly under the regulatory influence of growth factors and hormones, such as erythropoietin (EPO) for red cell production. EPO is required for the maintenance of committed erythroid progenitor cells which, in the absence of the hormone, undergo programmed cell death (apoptosis). The regulated process of red cell production is erythropoiesis, and its key elements are illustrated in Fig. 3.

 

 

Fig. 3. The physiologic regulation of red cell production by tissue oxygen tension.

 

 

 

In the bone marrow, the first morphologically recognizable erythroid precursor is the pronormoblast. This cell can undergo 4 to 5 cell divisions that result in the production of 16 to 32 mature red cells. With increased EPO production, or the administration of EPO as a drug, early progenitor cell numbers are amplified and, in turn, give rise to increased numbers of erythrocytes. The regulation of EPO production itself is linked to O2 transport.

In mammals, O2 is transported to tissues bound to the hemoglobin contained within circulating red cells. The mature red cell is 8um in diameter, anucleate, discoid in shape, and extremely pliable in order for it to traverse the microcirculation successfully; its membrane integrity is maintained by the intracellular generation of ATP. Normal red cell production results in the daily replacement of 0.8 to 1% of all circulating red cells in the body. The average red cell lives 100 to 120 days. The machinery responsible for red cell production is called the erythron. The erythron is a dynamic organ made up of a rapidly proliferating pool of marrow erythroid precursor cells and a large mass of mature circulating red blood cells. The size of the red cell mass reflects the balance of red cell production and destruction. The physiologic basis of red cell production and destruction provides an understanding of the mechanisms that can lead to anemia.

The physiologic regulator of red cell production, the glycoprotein hormone EPO, is produced and released by peritubular capillary lining cells within the kidney. These cells are highly specialized epithelial-like cells. A small amount of EPO is produced by hepatocytes. The fundamental stimulus for EPO production is the availability of O2 for tissue metabolic needs. Impaired O2 delivery to the kidney can result from a decreased red cell mass (anemia), impaired O2 loading of the hemoglobin molecule (hypoxemia), or, rarely, impaired blood flow to the kidney (renal artery stenosis). EPO governs the day-to-day production of red cells, and ambient levels of the hormone can be measured in the plasma by sensitive immunoassaysѕthe normal level being 10 to 25 U/L. When the hemoglobin concentration falls below 100 to 120 g/L (10 to 12 g/dL), plasma EPO levels increase logarithmically in inverse proportion to the severity of the anemia. In circulation, EPO has a half-clearance time of 6 to 9 h. EPO acts by binding to specific receptors on the surface of marrow erythroid precursors, inducing them to proliferate and to mature. Under the stimulus of EPO, red blood cell production can increase four- to fivefold within a 1- to 2-week period but only in the presence of adequate nutrients, especially iron. The functional capacity of the erythron, therefore, requires normal renal production of EPO, a functioning erythroid marrow, and an adequate supply of substrates for hemoglobin synthesis. A defect in any of these key components can lead to anemia. Generally, anemia is recognized in the laboratory when a patient's hemoglobin level or hematocrit is reduced below an expected value (the normal range). The likelihood and severity of anemia are defined based on the deviation of the patient's hemoglobin/hematocrit from values expected for age- and sex-matched normal subjects. The lower ranges of distribution of hemoglobin/hematocrit values for adult males and females are shown in Fig. 61-2. The hemoglobin concentration in adults has a Gaussian distribution. The mean hematocrit value for adult males is 47% (± SD 7) and that for adult females is 42% (± 5). Any individual hematocrit or hemoglobin value carries with it a likelihood of associated anemia. Thus, a hematocrit of Ј39% in an adult male or <35% in an adult female has only about a 25% chance of being normal. Suspected low hemoglobin or hematocrit values are more easily interpreted if there are historic values for the same patient for comparison.

The critical elements of erythropoiesis-EPO production, iron availability, the proliferative capacity of the bone marrow, and effective maturation of red cell precursors-are used for the initial classification of anemia.

 

STRUCTURE AND FUNCTION OF THE SPLEEN

The spleen is a reticuloendothelial organ that has its embryologic origin in the dorsal mesogastrium at about 5 weeks' gestation. It arises in a series of hillocks, migrates to its normal adult location in the left upper quadrant (LUQ), and is attached to the stomach via the gastrolienal ligament and to the kidney via the lienorenal ligament. When the hillocks fail to unify into a single tissue mass, accessory spleens may develop in around 20% of persons. The function of the spleen has been elusive. Galen believed it was the source of "black bile" or melancholia, and the word hypochondria (literally, beneath the ribs) and the idiom "to vent one's spleen" attest to the beliefs that the spleen had an important influence on the psyche and emotions. In humans, its normal physiologic roles seem to be the following:

1.  Maintenance of quality control over erythrocytes in the red pulp by removal of senescent and defective red blood cells. The spleen accomplishes this function through a unique organization of its parenchyma and vasculature.

2.  Synthesis of antibodies in the white pulp.

3.  The removal of antibody-coated bacteria and antibody-coated blood cells from the circulation.

An increase in these normal functions may result in splenomegaly.

The spleen is composed of red pulp and white pulp, which are Malpighi's terms for the red blood-filled sinuses and reticuloendothelial cell-lined cords and the white lymphoid follicles arrayed within the red pulp matrix. The spleen is in the portal circulation. The reason for this is unknown but may relate to the fact that lower blood pressure allows less rapid flow and minimizes damage to normal erythrocytes. Blood flows into the spleen at a rate of about 150 mL/min through the splenic artery, which ultimately ramifies into central arterioles. Some blood goes from the arterioles to capillaries and then to splenic veins and out of the spleen, but the majority of blood from central arterioles flows into the macrophage-lined sinuses and cords. The blood entering the sinuses reenters the circulation through the splenic venules, but the blood entering the cords is subjected to an inspection of sorts. In order to return to the circulation, the blood cells in the cords must squeeze through slits in the cord lining to enter the sinuses that lead to the venules. Old and damaged erythrocytes are less deformable and are retained in the cords, where they are destroyed and their components recycled. Red cell inclusion bodies such as parasites, nuclear residua (Howell-Jolly bodies), or denatured hemoglobin (Heinz bodies) are pinched off in the process of passing through the slits, a process called pitting. The culling of dead and damaged cells and the pitting of cells with inclusions appear to occur without significant delay since the blood transit time through the spleen is only slightly slower than in other organs.

The spleen is also capable of assisting the host in adapting to its hostile environment. It has at least three adaptational functions: (1) clearance of bacteria and particulates from the blood, (2) the generation of immune responses to certain invading pathogens, and (3) the generation of cellular components of the blood under circumstances in which the marrow is unable to meet the needs (i.e., extramedullary hematopoiesis). The latter adaptation is a recapitulation of the blood-forming function the spleen plays during gestation. In some animals, the spleen also serves a role in the vascular adaptation to stress because it stores red blood cells (often hemoconcentrated to higher hematocrits than normal) under normal circumstances and contracts under the influence of b-adrenergic stimulation to provide the animal with an autotransfusion and improved oxygen-carrying capacity. However, the normal human spleen does not sequester or store red blood cells and does not contract in response to sympathetic stimuli. The normal human spleen contains approximately one-third of the total body platelets and a significant number of marginated neutrophils. These sequestered cells are available when needed to respond to bleeding or infection.

 

Physical examination of lymph system.

 

LYMPHADENOPATHY

Lymphadenopathy may be an incidental finding in patients being examined for various reasons or it may be a presenting sign or symptom of the patient's illness. The physician must eventually decide whether the lymphadenopathy is a normal finding or one that requires further study, up to and including biopsy. Soft, flat, submandibular nodes (<1 cm) are often palpable in healthy children and young adults, and healthy adults may have palpable inguinal nodes of up to 2 cm, which are considered normal. Further evaluation of these normal nodes is not warranted. In contrast, if the physician believes the node(s) to be abnormal, then pursuit of a more precise diagnosis is needed.

Approach to the Patient

Lymphadenopathy may be a primary or secondary manifestation of numerous disorders.

 

Many of these disorders are infrequent causes of lymphadenopathy. Analysis of lymphadenopathy in primary care practice has shown that more than two-thirds of patients have nonspecific causes or upper respiratory illnesses (viral or bacterial), and fewer than 1% have a malignancy. In one study, researchers reported that 186 of 220 patients (84%) referred for evaluation of lymphadenopathy had a "benign" diagnosis. The remaining 34 patients (16%) had a malignancy (lymphoma or metastatic adenocarcinoma). Sixty-three percent (112) of the 186 patients with benign lymphadenopathy had a nonspecific or reactive etiology (no causative agent found), and the remainder had a specific cause demonstrated, most commonly infectious mononucleosis, toxoplasmosis, or tuberculosis. Thus, the vast majority of patients with lymphadenopathy will have a nonspecific etiology requiring few diagnostic tests.

Clinical Assessment  The physician will be aided in the pursuit of an explanation for the lymphadenopathy by a careful medical history, physical examination, selected laboratory tests, and perhaps an excisional lymph node biopsy.

The medical history should reveal the setting in which lymphadenopathy is occurring. Symptoms such as sore throat, cough, fever, night sweats, fatigue, weight loss, or pain in the nodes should be sought. The patient's age, sex, occupation, exposure to pets, sexual behavior, and use of drugs such as diphenylhydantoin are other important historic points. For example, children and young adults usually have benign (i.e., nonmalignant) disorders, such as viral or bacterial upper respiratory infections, infectious mononucleosis, toxoplasmosis, and, in some countries, tuberculosis, which account for the observed lymphadenopathy. In contrast, after age 50 the incidence of malignant disorders increases and that of benign disorders decreases.

The physical examination can provide useful clues such as the extent of lymphadenopathy (localized or generalized), size of nodes, texture, presence or absence of nodal tenderness, signs of inflammation over the node, skin lesions, and splenomegaly. A thorough ear, nose, and throat (ENT) examination is indicated in adult patients with cervical adenopathy and a history of tobacco use. Localized or regional adenopathy implies involvement of a single anatomic area. Generalized adenopathy has been defined as involvement of three or more noncontiguous lymph node areas. Many of the causes of lymphadenopathy (Table 63-1) can produce localized or generalized adenopathy, so this distinction is of limited utility in the differential diagnosis. Nevertheless, generalized lymphadenopathy is frequently associated with nonmalignant disorders such as infectious mononucleosis [Epstein-Barr virus (EBV) or cytomegalovirus (CMV)], toxoplasmosis, AIDS, other viral infections, systemic lupus erythematosus (SLE), and mixed connective tissue disease. Acute and chronic lymphocytic leukemias and malignant lymphomas also produce generalized adenopathy in adults.

The site of localized or regional adenopathy may provide a useful clue about the cause. Occipital adenopathy often reflects an infection of the scalp, and preauricular adenopathy accompanies conjunctival infections and cat-scratch disease. The most frequent site of regional adenopathy is the neck, and most of the causes are benign-upper respiratory infections, oral and dental lesions, infectious mononucleosis, other viral illnesses. The chief malignant causes include metastatic cancer from head and neck, breast, lung, and thyroid primaries. Enlargement of supraclavicular and scalene nodes is always abnormal. Because these nodes drain regions of the lung and retroperitoneal space, they can reflect either lymphomas, other cancers, or infectious processes arising in these areas. Virchow's node is an enlarged left supraclavicular node infiltrated with metastatic cancer from a gastrointestinal primary. Metastases to supraclavicular nodes also occur from lung, breast, testis, or ovarian cancers. Tuberculosis, sarcoidosis, and toxoplasmosis are nonneoplastic causes of supraclavicular adenopathy. Axillary adenopathy is usually due to injuries or localized infections of the ipsilateral upper extremity. Malignant causes include melanoma or lymphoma and, in women, breast cancer. Inguinal lymphadenopathy is usually secondary to infections or trauma of the lower extremities and may accompany sexually transmitted diseases such as lymphogranuloma venereum, primary syphilis, genital herpes, or chancroid. These nodes may also be involved by lymphomas and metastatic cancer from primary lesions of the rectum, genitalia, or lower extremities (melanoma).

The size and texture of the lymph node(s) and the presence of pain are useful parameters in evaluating a patient with lymphadenopathy. Nodes <1.0 cm² in area (1.0 x 1.0 cm or less) are almost always secondary to benign, nonspecific reactive causes. In one retrospective analysis of younger patients (9 to 25 years) who had a lymph node biopsy, a maximum diameter of >2 cm served as one discriminant for predicting that the biopsy would reveal malignant or granulomatous disease. Another study showed that a lymph node size of 2.25 cm² (1.5 cm x 1.5 cm) was the best discriminating limit for distinguishing malignant or granulomatous lymphadenopathy from other causes of lymphadenopathy. Patients with node(s) Ј1.0 cm2 should be observed after excluding infectious mononucleosis and/or toxoplasmosis unless there are symptoms and signs of an underlying systemic illness.

The texture of lymph nodes may be described as soft, firm, rubbery, hard, discrete, matted, tender, movable, or fixed. Tenderness is found when the capsule is stretched during rapid enlargement, usually secondary to an inflammatory process. Some malignant diseases such as acute leukemia may produce rapid enlargement and pain in the nodes. Nodes involved by lymphoma tend to be large, discrete, symmetric, rubbery, firm, mobile, and nontender. Nodes containing metastatic cancer are often hard, nontender, and nonmovable because of fixation to surrounding tissues. The coexistence of splenomegaly in the patient with lymphadenopathy implies a systemic illness such as infectious mononucleosis, lymphoma, acute or chronic leukemia, SLE, sarcoidosis, toxoplasmosis, cat-scratch disease, or other less common hematologic disorders. The patient's story should provide helpful clues about the underlying systemic illness.

Nonsuperficial presentations (thoracic or abdominal) of adenopathy are usually detected as the result of a symptom-directed diagnostic workup. Thoracic adenopathy may be detected by routine chest roentgenography or during the workup for superficial adenopathy. It may also be found because the patient complains of a cough or wheezing from airway compression; hoarseness from recurrent laryngeal nerve involvement; dysphagia from esophageal compression; or swelling of the neck, face, or arms secondary to compression of the superior vena cava or subclavian vein. The differential diagnosis of mediastinal and hilar adenopathy includes primary lung disorders and systemic illnesses that characteristically involve mediastinal or hilar nodes. In the young, mediastinal adenopathy is associated with infectious mononucleosis and sarcoidosis. In endemic regions, histoplasmosis can cause unilateral paratracheal lymph node involvement that mimics lymphoma. Tuberculosis can also cause unilateral adenopathy. In older patients, the differential diagnosis includes primary lung cancer (especially among smokers), lymphomas, metastatic carcinoma (usually lung), tuberculosis, fungal infection, and sarcoidosis.

Enlarged intraabdominal or retroperitoneal nodes are usually malignant. Although tuberculosis may present as mesenteric lymphadenitis, these masses usually contain lymphomas or, in young men, germ cell tumors.

 

Physical examination of the liver.

Patients with severe hemolysis usually present during early childhood with anemia, jaundice, and splenomegaly. Fever, splenomegaly, hepatomegaly, lymphadenopathy, sternal tenderness, and evidence of infection and hemorrhage are often found at diagnosis of leukemia.

Typical physical findings are icterus, hepatomegaly, hepatic tenderness, splenomegaly, palmar erythema. Signs of advanced disease include muscle-wasting, ascites, edema, dilated abdominal veins, hepatic fetor, asterixis, mental confusion, stupor, and coma.

Icterus is best appreciated by inspecting the sclera under natural light. In fair-skinned individuals, a yellow color of the skin may be obvious. In dark-skinned individuals, the mucous membranes below the tongue can demonstrate jaundice. Jaundice is rarely detectable if the serum bilirubin level is <43 umol/L (2.5 ug/dL) but may remain detectable below this level during recovery from jaundice (because of protein and tissue binding of conjugated bilirubin).

Hepatomegaly is the most reliable physical finding in examining the liver. Discomfort on touching or pressing on the liver should be carefully sought with percussive comparison of the right and left upper quadrants.

Splenomegaly occurs in many medical conditions but can be a subtle but significant physical finding in liver disease. The availability of ultrasound (US) assessment of the spleen allows for confirmation of the physical finding.

Several skin disorders and changes occur commonly in hematologic diseases.

 

Physical examination of the spleen.

Clinical Assessment. The most common symptoms produced by diseases involving the spleen are pain and a heavy sensation in the LUQ. Massive splenomegaly may cause early satiety.  Pain may result from acute swelling of the spleen with stretching of the capsule, infarction, or inflammation of the capsule. For many years, it was believed that splenic infarction was clinically silent, which at times is true. However, Soma Weiss, in his classic 1942 report of the self-observations by a Harvard medical student on the clinical course of subacute bacterial endocarditis, documented that severe LUQ and pleuritic chest pain may accompany thromboembolic occlusion of splenic blood flow. Vascular occlusion, with infarction and pain, is commonly seen in children with sickle cell crises. Rupture of the spleen, either from trauma or infiltrative disease that breaks the capsule, may result in intraperitoneal bleeding, shock, and death. The rupture itself may be painless.

A palpable spleen is the major physical sign produced by diseases affecting the spleen and suggests enlargement of the organ. The normal spleen is said to weigh less than 250 g, decreases in size with age, normally lies entirely within the rib cage, has a maximum cephalocaudad diameter of 13 cm by ultrasonography or maximum length of 12 cm and/or width of 7 cm by radionuclide scan, and is usually not palpable. However, a palpable spleen was found in 3% of 2200 asymptomatic, male, freshman college students. Follow-up at 3 years revealed that 30% of those students still had a palpable spleen without any increase in disease prevalence. Ten-year follow-up found no evidence for lymphoid malignancies. Furthermore, in some tropical countries (e.g., New Guinea) the incidence of splenomegaly may reach 60%. Thus, the presence of a palpable spleen does not always equate with presence of disease. Even when disease is present, splenomegaly may not reflect the primary disease, but rather a reaction to it. For example, in patients with Hodgkin's disease, only two-thirds of the palpable spleens show involvement by the cancer.

Physical examination of the spleen utilizes primarily the techniques of palpation and percussion. Inspection may reveal a fullness in the LUQ that descends on inspiration, a finding associated with a massively enlarged spleen. Auscultation may reveal a venous hum or a friction rub.

Palpation can be accomplished by bimanual palpation, ballotment, and palpation from above (Middleton maneuver). For bimanual palpation, which is at least as reliable as the other techniques, the patient is supine with flexed knees. The examiner's left hand is placed on the lower rib cage and pulls the skin toward the costal margin, allowing the fingertips of the right hand to feel the tip of the spleen as it descends while the patient inspires slowly, smoothly, and deeply. Palpation is begun with the right hand in the left lower quadrant with gradual movement toward the left costal margin, thereby identifying the lower edge of a massively enlarged spleen. When the spleen tip is felt, the finding is recorded as centimeters below the left costal margin at some arbitrary point, i.e., 10 to 15 cm, from the midpoint of the umbilicus or the xiphisternal junction. This allows other examiners to compare findings or the initial examiner to determine changes in size over time. Bimanual palpation in the right lateral decubitus position adds nothing to the supine examination.

Percussion for splenic dullness is accomplished with any of three techniques described by Nixon, Castell, or Barkun:

1.  Nixon's method: The patient is placed on the right side so that the spleen lies above the colon and stomach. Percussion begins at the lower level of pulmonary resonance in the posterior axillary line and proceeds diagonally along a perpendicular line toward the lower midanterior costal margin. The upper border of dullness is normally 6 to 8 cm above the costal margin. Dullness greater than 8 cm in an adult is presumed to indicate splenic enlargement.

2.  Castell's method: With the patient supine, percussion in the lowest intercostal space in the anterior axillary line (8th or 9th) produces a resonant note if the spleen is normal in size. This is true during expiration or full inspiration. A dull percussion note on full inspiration suggests splenomegaly.

3.  Percussion of Traube's semilunar space: The borders of Traube's space are the sixth rib superiorly, the left midaxillary line laterally, and the left costal margin inferiorly. The patient is supine with the left arm slightly abducted. During normal breathing, this space is percussed from medial to lateral margins, yielding a normal resonant sound. A dull percussion note suggests splenomegaly.

 

Studies comparing methods of percussion and palpation with a standard of ultrasonography or scintigraphy have revealed sensitivity of 56 to 71% for palpation and 59 to 82% for percussion. Reproducibility among examiners is better for palpation than percussion. Both techniques are less reliable in obese patients or patients who have just eaten. Thus, the physical examination techniques of palpation and percussion are imprecise at best. It has been suggested that the examiner perform percussion first and, if positive, proceed to palpation; if the spleen is palpable, then one can be reasonably confident that splenomegaly exists. However, not all LUQ masses are enlarged spleens; gastric or colon tumors and pancreatic or renal cysts or tumors can mimic splenomegaly.

The presence of an enlarged spleen can be more precisely determined, if necessary, by liver-spleen radionuclide scan, CT, MRI, or ultrasonography. The latter technique is the current procedure of choice for routine assessment of spleen size (normal = a maximum cephalocaudad diameter of 13 cm) because it has high sensitivity and specificity and is safe, noninvasive, quick, mobile, and less costly. Nuclear medicine scans are accurate, sensitive, and reliable but are costly, require greater time to generate data, and utilize immobile equipment. They have the advantage of demonstrating accessory splenic tissue. CT and MRI provide accurate determination of spleen size, but the equipment is immobile and the procedures are expensive. MRI appears to offer no advantage over CT. Changes in spleen structure such as mass lesions, infarcts, inhomogeneous infiltrates, and cysts are more readily assessed by CT, MRI, or ultrasonography. None of these techniques is very reliable in the detection of patchy infiltration (e.g., Hodgkin's disease).

 

 

 

The intra-abdominal physical exemination is shown in video 1  (http://intranet.tdmu.edu.ua/data/teacher/video/fiz_ob/Examination%20Of%20An%20Intra-abdominal%20Lump-(devlto).avi).

 

 

 

Sternal puncture, indications and diagnostic able.

 

Bone marrow examination is performed in adults either from sternum or posterior iliac crest. Marrow may be simply aspirated or a bone marrow biopsy (trephine) performed.

 

 

 

 

Pict. 6 A small amount of bone marrow is removed during a bone marrow aspiration. The procedure is uncomfortable, but can be tolerated by both children and adults. The marrow can be studied to determine the cause of anemia, the presence of leukemia or other malignancy, or the presence of some "storage diseases" in which abnormal metabolic products are stored in certain bone marrow cells.

 

 

 The latter cannot be obtained safely from the sternum and increasingly both aspirate and biopsy are performed from the posterior iliac crest. A biopsy is superior for assessing marrow cellularity and infiltration. Bone marrow examination is performed under local anaestethesia and can easily be undertaken as an outpatient procedure. Both aspiration and trephine biopsy can be carried out by the same needle but often separate needles are used.

 

 

Bone marrow aspiration and biopsy

 

 

Pict. 7. Bone marrow aspiration and biopsy. Patient position (superior posterior iliac crest).

 

 

 

Pict. 8. Bone marrow aspiration and biopsy. Bone marrow tray.

 

 

 

Pict. 9. Bone marrow aspiration and biopsy. Skin preparation.

 

 

 

Pict. 10. Bone marrow aspiration and biopsy. Site preparation.

 

 

 

Pict. 11. Bone marrow aspiration and biopsy. Local anesthetic.

 

 

 

Pict. 12. Bone marrow aspiration and biopsy. Aspiration needle placement.

 

 

 

Pict. 13. Bone marrow aspiration.

 

 

 

Pict. 14. Bone marrow biopsy. Jamshidi needle placement.

 

 

 

Pict. 15. Bone marrow biopsy. Jamshidi needle placement.

 

 

 

Pict. 16. Bone marrow biopsy specimen.

 

 

 

Pict. 17. Bone marrow biopsy specimen.

 

 

 

Pict. 18. Bone marrow biopsy specimen in fixative solution.

 

 

 

Pict. 19. Bone marrow aspiration and biopsy slide preparation.

 

 

 

Pict. 20. Bone marrow aspiration and biopsy slide preparation.

 

 

 

Pict. 21. Bone marrow aspiration and biopsy slides prior to staining.

 

 

 

 

 

Marrow examined not only for its morphological appearances but increasingly cell marker studies, karyotyping and molecular biology studies are undertaken as appropriate for the accurate diagnosis and assessement of malignant disease. Marrow can also be sent for culture in cases of suspected tuberculosis. The main indications for a bone marrow examination are shown in the table 1.

 

 

Table 1. Main indications for bone marrow examination

Marrow infiltration:

Leukemia/lymphoma

Secondary carcinoma

Myelofibrosis

Cytopenia:

Neutropenia

Thrombocytopenia

Anemia-complex cases or aplasia

 

 

Myeloproliferative disorders

 

Aplastic anemia. Bone Marrow. The bone marrow is usually readily aspirated but appears dilute on smear, and the fatty biopsy specimen may be grossly pale on withdrawal; a "dry tap" suggests fibrosis or myelophthisis. In severe aplasia the smear of the aspirated specimen shows only red cells, residual lymphocytes, and stromal cells; the biopsy, which should be >1 cm in length, is superior for determination of cellularity and shows mainly fat under the microscope, with hematopoietic cells occupying, by definition, <25% of the marrow space. In the most serious cases the biopsy is virtually 100% fat. The correlation between marrow cellularity and disease severity is imperfect. Some patients with moderate disease by blood counts will have empty iliac crest biopsies, while "hot spots" of hematopoiesis may be seen in severe cases. If an iliac crest specimen is inadequate, cells should also be obtained by aspiration from the sternum. Residual hematopoietic cells should have normal morphology, except for mildly megaloblastic erythropoiesis; megakaryocytes are invariably greatly reduced and usually absent. Areas adjacent to the spicule should be searched for myeloblasts. Granulomas (in cellular specimens) may indicate an infectious etiology of the marrow failure.

 

The myelodysplastic syndromes. Bone Marrow.  The bone marrow is usually normal or hypercellular but in 20% of cases is sufficiently hypocellular to be confused with aplasia. No single characteristic feature of marrow morphology distinguishes MDS, but the following are commonly observed: dyserythropoietic changes (especially nuclear abnormalities) and ringed sideroblasts in the erythroid lineage; hypogranulation and hyposegmentation in granulocytic precursors, with an increase in myeloblasts; and megakaryocytes showing reduced numbers of disorganized nuclei. Prognosis strongly correlates with the proportion of marrow blasts. Cytogenetic analysis also is important. A much more sensitive method to detect infrequent chromosome aberrations is fluorescent in situ hybridization, and gene amplification by polymerase chain reaction can detect known chromosomal translocations.

 

Polycythemia vera. A bone marrow aspirate and biopsy will provide no specific diagnostic information, and unless there is a need to establish the presence of myelofibrosis or exclude some other disorder, these procedures need not be done. Although the presence of a cytogenetic abnormality such as trisomy 8 or 9 or 20q- in the setting of an expansion of the red cell mass supports the clonal etiology, no specific cytogenetic abnormality is associated with polycythemia vera, and the absence of a cytogenetic marker does not exclude the diagnosis.

 

Acute myeloid leukaemia. The diagnosis of AML is established by the presence of >20% myeloblasts in blood and/or bone marrow. Myeloblasts have nuclear chromatin that is uniformly fine or lacelike in appearance and large nucleoli (two to five per cell). If specific cytoplasmic granules, Auer rods, or the nuclear folding and clefting characteristic of monocytoid cells are not present, the morphologic features observed under light microscopy may not be sufficient to clarify the diagnosis. A positive myeloperoxidase reaction in >3% of the blasts may be the only feature distinguishing AML from acute lymphoblastic leukemia (ALL).

 

Precursor B Cell Lymphoblastic Leukemia/Lymphoma . The diagnosis is usually made by bone marrow biopsy, which shows infiltration by malignant lymphoblasts. Demonstration of a pre-B cell immunophenotype and, often, characteristic cytogenetic abnormalities confirm the diagnosis. An adverse prognosis in patients with precursor B cell ALL is predicted by a very high white cell count, the presence of symptomatic CNS disease, and unfavorable cytogenetic abnormalities. For example, t(9;22) is frequently found in adults with B cell lymphoblastic leukemia and is associated with a very poor outlook.

 

B Cell Chronic Lymphoid Leukemia/Small Lymphocytic. Confirmation of bone marrow infiltration by the same cells confirms the diagnosis. The peripheral blood smear in such patients typically shows many "smudge" or "basket" cells, nuclear remnants of cells damaged by the physical shear stress of making the blood smear. If cytogenetic studies are performed, trisomy 12 is found in ~25 to 30% of patients. Abnormalities in chromosome 13 are also seen.

 

Puncture of the lymph node.

The indications for lymph node biopsy are imprecise, yet it is a valuable diagnostic tool. The decision to biopsy may be made early in a patient's evaluation or delayed for up to 2 weeks. Prompt biopsy should occur if the patient's history and physical findings suggest a malignancy; examples include a solitary, hard, nontender cervical node in an older patient who is a chronic user of tobacco; supraclavicular adenopathy; and solitary or generalized adenopathy that is firm, movable, and suggestive of lymphoma. If a primary head and neck cancer is suspected as the basis of a solitary, hard cervical node, then a careful ENT examination should be performed. Any mucosal lesion that is suspicious for a primary neoplastic process should be biopsied first. If no mucosal lesion is detected, an excisional biopsy of the largest node should be performed. Fine-needle aspiration should not be performed as the first diagnostic procedure. Most diagnoses require more tissue than such aspiration can provide and it often delays a definitive diagnosis. Fine-needle aspiration should be reserved for thyroid nodules and for confirmation of relapse in patients whose primary diagnosis is known. If the primary physician is uncertain about whether to proceed to biopsy, consultation with a hematologist or medical oncologist should be helpful. In primary care practices, fewer than 5% of lymphadenopathy patients will require a biopsy. That percentage will be considerably larger in referral practices, i.e., hematology, oncology, or otolaryngology (ENT).

Two groups have reported algorithms that they claim will identify more precisely those lymphadenopathy patients who should have a biopsy. Both reports were retrospective analyses in referral practices. The first study involved patients 9 to 25 years of age who had a node biopsy performed. Three variables were identified that predicted those young patients with peripheral lymphadenopathy who should undergo biopsy; lymph node size >2 cm in diameter and abnormal chest x-ray had positive predictive value, whereas recent ENT symptoms had negative predictive values. The second study evaluated 220 lymphadenopathy patients in a hematology unit and identified five variables [lymph node size, location (supraclavicular or non-supraclavicular), age (>40 years or <40 years), texture (nonhard or hard), and tenderness] that were utilized in a mathematical model to identify those patients requiring a biopsy. Positive predictive value was found for age >40 years, supraclavicular location, node size >2.25 cm2, hard texture, and lack of pain or tenderness. Negative predictive value was evident for age <40 years, node size <1.0 cm2, nonhard texture, and tender or painful nodes. Ninety-one percent of those who required biopsy were correctly classified by this model. Since both of these studies were retrospective analyses and one was limited to young patients, it is not known how useful these models would be if applied prospectively in a primary care setting.

 

Blood analysis, coagulogram, their diagnostic able.

 

PERIPHERAL BLOOD SMEAR

The peripheral blood smear provides important information about defects in red cell production. As a complement to the red cell indices, the blood smear also reveals variations in cell size (anisocytosis) and shape (poikilocytosis). The degree of anisocytosis usually correlates with increases in the RDW or the range of cell sizes. Poikilocytosis suggests a defect in the maturation of red cell precursors in the bone marrow or fragmentation of circulating red cells. The blood smear may also reveal polychromasiaѕred cells that are slightly larger than normal and grayish blue in color on the Wright-Giemsa stain. These cells are reticulocytes that have been prematurely released from the bone marrow, and their color represents residual amounts of ribosomal RNA. These cells appear in circulation in response to EPO stimulation or to architectural damage of the bone marrow (fibrosis, infiltration of the marrow by malignant cells, etc.) that results in their disordered release from the marrow. The appearance of nucleated red cells, Howell-Jolly bodies, target cells, sickle cells, and others may provide clues to specific disorders. Laboratory tests in anemia diagnosis are shown in table 2.

 

 

 

Anemias associated with normocytic and normochromic red cells and an inappropriately low reticulocyte response (reticulocyte index <2.5) are hypoproliferative anemias. This category includes early iron deficiency (before hypochromic microcytic red cells develop), acute and chronic inflammation (including many malignancies), renal disease, hypometabolic states such as protein malnutrition and endocrine deficiencies, and anemias from marrow damage.

 

Sickle Cell Anemia. Most patients with sickling syndromes suffer from hemolytic anemia, with hematocrits of 15 to 30%, and significant reticulocytosis. Anemia was once thought to exert protective effects against vasoocclusion by reducing blood viscosity. Natural history and drug therapy trials suggest that an increase in the hematocrit with feedback inhibition of reticulocytosis might be beneficial, even at the expense of increased blood viscosity. The role of adhesive reticulocytes in vasoocclusion might account for these paradoxical effects.

Granulocytosis is common. The white cell count can fluctuate substantially and unpredictably during and between painful crises, infectious episodes, and other intercurrent illnesses.

The finding of significant macrocytosis [mean corpuscular volume (MCV) > 100 fL] suggests the presence of a megaloblastic anemia. Other causes of macrocytosis include hemolysis, liver disease, alcoholism, hypothyroidism, and aplastic anemia. If the macrocytosis is marked (MCV > 110 fL), the patient is much more likely to have a megaloblastic anemia. Macrocytosis is less marked with concurrent iron deficiency or thalassemia. The reticulocyte count is low, and the leukocyte and platelet count may also be decreased, particularly in severely anemic patients. The blood smear (see Plate V-24) demonstrates marked anisocytosis and poikilocytosis, together with macroovalocytes, which are large, oval, fully hemoglobinized erythrocytes typical of megaloblastic anemias. There is some basophilic stippling, and an occasional nucleated RBC may be seen. In the white blood cell series, the neutrophils show hypersegmentation of the nucleus (see Plate V-38). This is such a characteristic finding that a single cell with a nucleus of six lobes or more should raise the immediate suspicion of a megaloblastic anemia. A rare myelocyte may also be seen. Bizarre, misshapen platelets are also observed. The reticulocyte index is low.

An elevated reticulocyte count in the patient with anemia is the most useful indicator of hemolysis, reflecting erythroid hyperplasia of the bone marrow; biopsy of the bone marrow is often unnecessary. Reticulocytes are also elevated in patients with active blood loss, those with myelophthisis, and those who are recovering from suppression of erythropoiesis.

 

Aplastic anemia. The smear shows large erythrocytes and a paucity of platelets and granulocytes. Mean corpuscular volume (MCV) is commonly increased. Reticulocytes are absent or few, and lymphocyte numbers may be normal or reduced. The presence of immature myeloid forms suggests leukemia or MDS; nucleated red blood cells suggest marrow fibrosis or tumor invasion; abnormal platelets suggest either peripheral destruction or MDS.

 

The myelodysplastic syndromes. Anemia is present in the majority of cases, either alone or as part of bi- or pancytopenia; isolated neutropenia or thrombocytopenia is more unusual. Macrocytosis is common, and the smear may be dimorphic with a distinctive population of large red blood cells. Platelets are also large and lack granules. In functional studies, they may show marked abnormalities, and patients may have bleeding symptoms despite seemingly adequate numbers. Neutrophils are hypogranulated; have hyposegmented, ringed, or abnormally segmented nuclei; and contain Dohle bodies and may be functionally deficient. Circulating myeloblasts usually correlate with marrow blast numbers, and their quantitation is important for classification and prognosis. The total white blood cell count is usually normal or low, except in chronic myelomonocytic leukemia. As in aplastic anemia, MDS also can be associated with a clonal population of PNH cells.

 

Polycythemia vera. Once the presence of absolute erythrocytosis has been established, its cause must be determined. An elevated plasma erythropoietin level suggests either an hypoxic cause for erythrocytosis or autonomous erythropoietin production, in which case assessment of pulmonary function and an abdominal computed tomography scan to evaluate renal and hepatic anatomy are appropriate. A normal erythropoietin level does not exclude an hypoxic cause for erythrocytosis. In polycythemia vera, in contrast to hypoxic erythrocytosis, the arterial oxygen saturation is normal. However, a normal oxygen saturation does not exclude a high-affinity hemoglobin as a cause for erythrocytosis, and it is here that documentation of previous hemoglobin levels and a family study become important. Because there is no clonal marker for polycythemia vera, clinical guidelines have been proposed to define the disease. A modified version is provided in Table 110-2. However, these guidelines do not establish clonality, and in some patients only with time will the underlying disorder become apparent. Diagnostic ambiguity does not preclude the initiation of therapy.

 

Other laboratory studies that may aid in diagnosis include the red cell count, mean corpuscular volume, and red cell distribution width (RDW). Only three situations cause microcytic erythrocytosis: b-thalassemia trait, hypoxic erythrocytosis, and polycythemia vera. However, with b-thalassemia trait the RDW is normal, whereas with hypoxic erythrocytosis and polycythemia vera, the RDW is usually elevated. A properly made blood smear from a patient with erythrocytosis will be virtually unreadable due to the marked elevation in red cell count, but no specific morphologic abnormalities are seen in the leukocytes or platelets in polycythemia vera.

The complete blood count can provide useful data for the diagnosis of acute or chronic leukemias, EBV or CMV mononucleosis, lymphoma with a leukemic component, pyogenic infections, or immune cytopenias in illnesses such as SLE.

Certain viral infections impair mononuclear phagocyte function. For example, influenza virus infection causes abnormal monocyte chemotaxis. Mononuclear phagocytes can be infected by HIV using CCR5, the chemokine receptor that acts as a coreceptor with CD4 for HIV. T lymphocytes produce IFN-g, which induces FcR expression and phagocytosis and stimulates hydrogen peroxide production by mononuclear phagocytes and neutrophils. In certain diseases, such as AIDS, IFN-g production may be deficient, while in other diseases, such as T cell lymphomas, excessive release of IFN-g may be associated with erythrophagocytosis by splenic macrophages.

Monocytopenia occurs with acute infections, with stress, and after treatment with glucocorticoids. Monocytopenia also occurs in aplastic anemia, hairy cell leukemia, acute myeloid leukemia, and as a direct result of myelotoxic drugs.

Eosinophilia is the presence of >500 eosinophils per microliter of blood and is common in many settings besides parasite infection.

Acute myeloid leukaemia. The median presenting leukocyte count is about 15,000/uL. Twenty-five to 40% of patients have counts <5000/uL, and 20% have counts >100,000/uL. Fewer than 5% have no detectable leukemic cells in the blood. Poor neutrophil function may be noted functionally by impaired phagocytosis and migration and morphologically by abnormal lobulation and deficient granulation.

Platelet counts <100,000/uL are found at diagnosis in ~75% of patients, and about 25% have counts <25,000/uL. Both morphologic and functional platelet abnormalities can be observed, including large and bizarre shapes with abnormal granulation and inability of platelets to aggregate or adhere normally to one another.

B Cell Chronic Lymphoid Leukemia/Small Lymphocytic. The diagnosis of typical B cell CLL is made when an increased number of circulating lymphocytes (i.e., >4 ґ 109/L and usually >10 ґ 109/L) is found that are monoclonal B cells and display the CD5 antigen.

 

The most important screening tests of the primary hemostatic system are (1) a bleeding time (a sensitive measure of platelet function), and (2) a platelet count. The latter correlates well with the propensity to bleed. The normal platelet count is 150,000 to 450,000/uL of blood. As long as the count is >100,000/uL, patients are usually not symptomatic and the bleeding time remains normal. Platelet counts of 50,000 to 100,000/uL cause mild prolongation of the bleeding time; bleeding occurs only from severe trauma or other stress. Patients with platelet counts <50,000/uL have easy bruising, manifested by skin purpura after minor trauma and bleeding after mucous membrane surgery. Patients with a platelet count <20,000/uL have an appreciable incidence of spontaneous bleeding, usually have petechiae, and may have intracranial or other spontaneous internal bleeding. Plasma coagulation function is readily assessed with the PTT, prothrombin time (PT), thrombin time (TT), and quantitative fibrinogen determination. The PTT screens the intrinsic limb of the coagulation system and tests for the adequacy of factors XII, HMWK, PK, XI, IX, and VIII. The PT screens the extrinsic or tissue factor-dependent pathway. Both tests also evaluate the common coagulation pathway involving all the reactions that occur after the activation of factor X. Prolongation of the PT and PTT that does not resolve after the addition of normal plasma suggests a coagulation inhibitor. A specific test for the conversion of fibrinogen to fibrin is needed when both the PTT and PT are prolonged-either a TT or a clottable fibrinogen level can be employed. When abnormalities are noted in any of the screening tests, more specific coagulation factor assays can be ordered to determine the nature of the defect.

Several rare coagulation abnormalities that may be missed as they do not affect these screening tests: factor XIII deficiency, a2 plasmin inhibitor deficiency, PAI-1 deficiency (PAI-1 is the major inhibitor of plasminogen activators), and Scott's syndrome, a platelet coagulant defect. A test for factor XIII-dependent fibrin cross-linking, such as clot solubility in 5 M urea, should be ordered when the PT and PTT are both normal but the history of bleeding is strong. The fibrinolytic system can be assessed by measuring the rate of clot lysis with the euglobulin lysis or whole blood clot lysis tests and by measuring the levels of a2 plasmin inhibitor and PAI-1. Scott's syndrome can be detected by measuring the serum PT, which assesses the amount of residual prothrombin.

Conditions associated with thrombosis are listed in Table 62-5. Patients suspected of having a hypercoagulable or prethrombotic disorder on the basis of clinical information should be tested with specific assays to screen for the known defects. Currently available tests can identify 50 to 60% of the cases of familial or recurrent venous thrombosis.

 

 

1. Anemia, definition.

Anemia is present in adults if the hematocrit is less than 41 % (haemoglobin < 13.5 g/dL) in males or 37 % (haemoglobin < 12 g/dL) in females.

 

 

 

 

Pict. 1 Blood is the only fluid tissue in the body. Blood transports oxygen and nutrients to body tissues, and returns waste and carbon dioxide. Blood distributes nearly everything that is carried from one area in the body to another place within the body. For instance, hormones are transported from the endocrine organs to their target organs. Blood helps maintain body temperature and normal pH levels in body tissues. The protective functions of blood include clot formation and the prevention of infection.

 

 

2. Clinical manifestations of anemias.

2.1.            Anemic syndrome.

Symptoms of anemia are easy fatigability, tachycardia, palpitations, tachypnea on exertion, pallor, malaise, weakness, light-headedness, vertigo, and tinnitus, as well as palpitations, angina, and the symptoms of congestive failure.

In the anemic patient, physical examination may demonstrate a forceful heartbeat, strong peripheral pulses, and a systolic "flow" murmur. The skin and mucous membranes may be pale if the hemoglobin is <80 to 100 g/L (8 to 10 g/dL).

 

 

 

Pict. 2. Hemoglobin is the most important component of red blood cells. It is composed of a protein called heme, which binds oxygen. In the lungs, oxygen is exchanged for carbon dioxide.

 

2.2. Sideropenic syndrome.

Cheilosis (fissures at the corners of the mouth), fever and koilonychia (spooning of the fingernails) are signs of advanced tissue iron deficiency.

Iron deficiency causes skin and mucosal changes, including a smooth tongue, brittle nails. Dysphagia because of formation of esophageal webs also occurs. Many iron-deficient patients develop pica, craving for specific foods, often not rich in iron.

 

2.3. Neurologic manifestations.

The neurologic manifestations often fail to remit fully on treatment. They begin pathologically with demyelination, followed by axonal degeneration and eventual neuronal death; the final stage, of course, is irreversible. Sites of involvement include peripheral nerves; the spinal cord, where the posterior and lateral columns undergo demyelination; and the cerebrum itself. Signs and symptoms include numbness and paresthesia in the extremities (the earliest neurologic manifestations), weakness, and ataxia. There may be sphincter disturbances. Reflexes may be diminished or increased. The Romberg and Babinski signs may be positive, and position and vibration senses are usually diminished. Disturbances of mentation will vary from mild irritability and forgetfulness to severe dementia or frank psychosis. It should be emphasized that neurologic disease may occur in a patient with a normal hematocrit and normal RBC indexes. Although it has many benefits, folate supplementation of food

The clinical features of cobalamin deficiency involve the blood, the gastrointestinal tract, and the nervous system.

 

2.4. Gastrointestinal manifestations.

The gastrointestinal manifestations reflect the effect of cobalamin deficiency on the rapidly proliferating gastrointestinal epithelium. The patient sometimes complains of a sore tongue, which on inspection will be smooth and beefy red. Anorexia with moderate weight loss may also be evident, possibly accompanied by diarrhea and other gastrointestinal symptoms. These latter manifestations may be caused in part by megaloblastosis of the small intestinal epithelium, which results in malabsorption.

 

2.5. Cytopenic syndrome.

Aplastic anemia can appear with seeming abruptness or have a more insidious onset. Bleeding is the most common early symptom; a complaint of days to weeks of easy bruising, oozing from the gums, nose bleeds, heavy menstrual flow, and sometimes petechiae will have been noticed. With thrombocytopenia, massive hemorrhage is unusual, but small amounts of bleeding in the central nervous system can result in catastrophic intracranial or retinal hemorrhage. Symptoms of anemia are also frequent, including lassitude, weakness, shortness of breath, and a pounding sensation in the ears. Infection is an unusual first symptom in aplastic anemia (unlike in agranulocytosis, where pharyngitis, anorectal infection, or frank sepsis occur early). A striking feature of aplastic anemia is the restriction of symptoms to the hematologic system, and patients often feel and look remarkably well despite drastically reduced blood counts. Systemic complaints and weight loss should point to other etiologies of pancytopenia. History of drug use, chemical exposure, and preceding viral illnesses must often be elicited with repeated questioning.

 

2.6. Hemolytic syndrome.

The hematologic manifestations are almost entirely the result of anemia, although very rarely purpura may appear, due to thrombocytopenia. Symptoms of anemia may include weakness, light-headedness, vertigo, and tinnitus, as well as palpitations, angina, and the symptoms of congestive failure. On physical examination, the patient with florid cobalamin deficiency is pale, with slightly icteric skin and eyes. Elevated bilirubin levels are related to high erythroid cell turnover in the marrow. The pulse is rapid, and the heart may be enlarged; auscultation will usually reveal a systolic flow murmur.

Hemolytic anemias present in different ways. Some appear suddenly as an acute, self-limited episode of intravascular or extravascular hemolysis, a presentation pattern often seen in patients with autoimmune hemolysis or with inherited defects of the Embden-Myerhof pathway or the glutathione reductase pathway. Patients with inherited disorders of the hemoglobin molecule or red cell membrane generally have a lifelong clinical history typical of the disease process. Those with chronic hemolytic disease, such as hereditary spherocytosis, may actually present not with anemia but with a complication stemming from the prolonged increase in red cell destruction such as aplastic crisis, symptomatic bilirubin gallstones, or splenomegaly.

The differential diagnosis of an acute or chronic hemolytic event requires the careful integration of family history, pattern of clinical presentation, and a number of highly specific laboratory studies. Some of the more common congenital hemolytic anemias may be identified from the red cell morphology, a routine laboratory test such as hemoglobin electrophoresis, or a screen for red cell enzymes. Acquired defects in red cell survival are often immunologically mediated and require the immunoglobulin test or a cold agglutinin titer to detect the presence of hemolytic antibodies or complement-mediated red cell destruction.

With acute hemolytic disease, the signs and symptoms depend on the mechanism that leads to red cell destruction. Intravascular hemolysis with release of free hemoglobin may be associated with acute back pain, free hemoglobin in the plasma and urine, and renal failure. Symptoms associated with more chronic or progressive anemia depend on the age of the patient and the adequacy of blood supply to critical organs. Symptoms associated with moderate anemia include fatigue, loss of stamina, breathlessness, and tachycardia (particularly with physical exertion). However, because of the intrinsic compensatory mechanisms that govern the O2-hemoglobin dissociation curve, the gradual onset of anemiaѕparticularly in young patientsѕmay not be associated with signs or symptoms until the anemia is severe [hemoglobin <70 to 80 g/L (7 to 8 g/dL)]. When anemia develops over a period of days or weeks, the total blood volume is normal to slightly increased and changes in cardiac output and regional blood flow help compensate for the overall loss in O2-carrying capacity. Changes in the position of the O2-hemoglobin dissociation curve account for some of the compensatory response to anemia. With chronic anemia, intracellular levels of 2,3-bisphosphoglycerate (BPG) rise, shifting the dissociation curve to the right and facilitating O2 unloading. This compensatory mechanism can only maintain normal tissue O2 delivery in the face of a 20 to 30 g/L (2 to 3 g/dL) deficit in hemoglobin concentration. Finally, further protection of O2 delivery to vital organs is achieved by the shunting of blood away from organs that are relatively rich in blood supply, particularly the kidney, gut, and skin.

 

 

3.        Classification of anemias.

 

 

 

 

Pict. 3 Blood & Lymphocyte Development

 

 

3.1.            Pathogenetic classification

3.2.            Morphogenic classification.

3.3.            International classification.

Initial Classification of Anemia  Classifying an anemia according to the functional defect in red cell production helps organize the subsequent use of laboratory studies. The three major classes of anemia are:

1) marrow production defects (hypoproliferation),

2) red cell maturation defects (ineffective erythropoiesis),

3) decreased red cell survival (blood loss/hemolysis).

This functional classification of anemia then guides the selection of specific clinical and laboratory studies designed to complete the differential diagnosis and to plan appropriate therapy.

 

 

The classification is shown in Fig. 1.

 

 

 

A hypoproliferative anemia is typically seen with a low reticulocyte production index together with little or no change in red cell morphology (a normocytic, normochromic anemia). Maturation disorders typically have a slight to moderately elevated reticulocyte production index that is accompanied by either macrocytic or microcytic red cell indices. Increased red blood cell destruction secondary to hemolysis results in an increase in the reticulocyte production index to at least three times normal, provided sufficient iron is available for hemoglobin synthesis. Hemorrhagic anemia does not typically result in production indices of more than 2.5 times normal because of the limitations placed on expansion of the erythroid marrow by iron availability.

 

 

 

Pict. 4 Sickle cell anemia is an inherited blood disease in which the red blood cells produce abnormal pigment (hemoglobin). The abnormal hemoglobin causes deformity of the red blood cells into crescent or sickle-shapes, as seen in this photomicrograph.

 

 

Pict.5. Elliptocytosis is a hereditary disorder of the red blood cells (RBCs). In this condition, the RBCs assume an elliptical shape, rather than the typical round shape.

 

 

Pict.6 Spherocytosis is a hereditary disorder of the red blood cells (RBCs), which may be associated with a mild anemia. Typically, the affected RBCs are small, spherically shaped, and lack the light centers seen in normal, round RBCs.

 

 

Pict. 7. Sickle cell anemia is an inherited disorder in which abnormal hemoglobin (the red pigment inside red blood cells) is produced. The abnormal hemoglobin causes red blood cells to assume a sickle shape, like the ones seen in this photomicrograph.

 

 

Pict. 8 Red blood cells (RBCs) are normally round. In ovalocytosis, the cells are oval. Other conditions that produce abnormally shaped RBCs include spherocytosis and eliptocytosis.

 

 

Pict. 9 These crescent or sickle-shaped red blood cells (RBCs) are present with Sickle cell anemia, and stand out clearly against the normal round RBCs. These abnormally shaped cells may become entangled and block blood flow in the small blood vessels (capillaries).

 

 

Pict. 10 This photomicrograph of red blood cells (RBCs) shows both sickle-shaped and pappenheimer bodies.

 

 

Pict. 11 These abnormal red blood cells (RBCs) resemble targets. These cells are seen in association with some forms of anemia, and following the removal of the spleen (splenectomy).

 

 

 

 

Pict.12. Peripheral smear showing multiple inclusion bodies inside the red blood cells.

 

 

4.        Iron deficiency anemia.

4.1.            Negative iron balance.

4.2.            Criteria for iron deficiency anemia.

4.3.            Differential diagnosis of the iron deficiency anemia.

4.4.            Treatment of the iron deficiency anemia.

 

 

STAGES OF IRON DEFICIENCY

Iron deficiency anemia is the condition in which there is anemia and clear evidence of iron deficiency. However, it is worthwhile to consider the steps by which iron deficiency occurs.

These can be divided into three stages. The first stage is negative iron balance, in which the demands for (or losses of) iron exceed the body's ability to absorb iron from the diet. This stage can result from a number of physiologic mechanisms including blood loss, pregnancy (in which the demands for red cell production by the fetus outstrip the mother's ability to provide iron), rapid growth spurts in the adolescent, or inadequate dietary iron intake. Most commonly, the growth needs of the fetus or rapidly growing child exceed the individual's ability to absorb the iron necessary for hemoglobin synthesis from the diet. Blood loss in excess of 10 to 20 mL of red cells per day is greater than the amount of iron that the gut can absorb from a normal diet. Under these circumstances the iron deficit must be made up by mobilization of iron from RE storage sites. During this period measurements of iron storesѕsuch as the serum ferritin level or the appearance of stainable iron on bone marrow aspirationsѕwill decrease. As long as iron stores are present and can be mobilized, the serum iron, total iron-binding capacity (TIBC), and red cell protoporphyrin levels remain within normal limits. At this stage, red cell morphology and indices are normal.

When iron stores become depleted, the serum iron begins to fall. Gradually, the TIBC increases, as do red cell protoporphyrin levels. By definition, marrow iron stores are absent when the serum ferritin level <15 ug/L. As long as the serum iron remains within the normal range, hemoglobin synthesis is unaffected despite the dwindling iron stores. Once the transferrin saturation falls to 15 to 20%, hemoglobin synthesis becomes impaired. This is a period of iron-deficient erythropoiesis. Careful evaluation of the peripheral blood smear reveals the first appearance of microcytic cells, and if the laboratory technology is available, one finds hypochromic reticulocytes in circulation. Gradually, the hemoglobin and hematocrit begin to fall, reflecting iron deficiency anemia. The transferrin saturation at this point is 10 to 15%.

When moderate anemia is present (hemoglobin 10-13 g/dL), the bone marrow remains hypoproliferative. With more severe anemia (hemoglobin 7-8 g/dL), hypochromia and microcytosis become more prominent, misshapen red cells (poikilocytes) appear on the blood smear as cigar or pencil-shaped forms and target cells, and the erythroid marrow becomes increasingly ineffective. Consequently, with severe prolonged iron deficiency anemia, erythroid hyperplasia of the marrow develops rather than hypoproliferation.

 

CAUSES OF IRON DEFICIENCY

Conditions that increase demand for iron, increase iron loss, or decrease iron intake, absorption, or use can produce iron deficiency.

 

 

 

 

 

CLINICAL PRESENTATION OF IRON DEFICIENCY

Certain clinical conditions carry an increased likelihood of iron deficiency. Pregnancy, adolescence, periods of rapid growth, and an intermittent history of blood loss of any kind should alert the clinician to possible iron deficiency. A cardinal rule is that the appearance of iron deficiency in an adult male means gastrointestinal blood loss until proven otherwise. Signs related to iron deficiency depend upon the severity and chronicity of the anemia in addition to the usual signs of anemia-fatigue, pallor, and reduced exercise capacity. Cheilosis (fissures at the corners of the mouth) and koilonychia (spooning of the fingernails) are signs of advanced tissue iron deficiency. The diagnosis of iron deficiency is typically based on laboratory results.

 

 

 

 

 

LABORATORY IRON STUDIES

Serum Iron and Total Iron-Binding Capacity  The serum iron level represents the amount of circulating iron bound to transferrin. The total iron-binding capacity (TIBC) is an indirect measure of the circulating transferrin. The normal range for the serum iron is 50 to 150 ug/dL; the normal range for TIBC is 300 to 360 ug/dL. Transferrin saturation, which is normally 25 to 50%, is obtained by the following formula: serum iron x 100 : TIBC. Iron deficiency states are associated with saturation levels below 18%. In evaluating the serum iron, the clinician should be aware that there is a diurnal variation in the value. A transferrin saturation rate of >50% indicates that a disproportionate amount of the iron bound to transferrin is being delivered to nonerythroid tissues. If this condition persists for an extended time, tissue iron overload may occur.

Serum Ferritin. Free iron is toxic to cells, and the body has established an elaborate set of protective mechanisms to bind iron in various tissue compartments. Within cells, iron is stored complexed to protein as ferritin or hemosiderin. Apoferritin binds to free ferrous iron and stores it in the ferric state. As ferritin accumulates within cells of the RE system, protein aggregates are formed as hemosiderin. Iron in ferritin or hemosiderin can be extracted for release by the RE cells although hemosiderin is less readily available. Under steady state conditions, the serum ferritin level correlates with total body iron stores; thus, the serum ferritin level is the most convenient laboratory test to estimate iron stores. The normal value for ferritin varies according to the age and gender of the individual (Fig. 1). Adult males have serum ferritin values averaging about 100 ug/L, while adult females have levels averaging 30 ug/L. As iron stores are depleted, the serum ferritin falls to <15 ug/L. Such levels are virtually always diagnostic of absent body iron stores.

Evaluation of Bone Marrow Iron Stores. Although RE cell iron stores can also be estimated from the iron stain of a bone marrow aspirate or biopsy, the measurement of serum ferritin has largely supplanted bone marrow aspirates for determination of storage iron (Table 1). The serum ferritin level is a better indicator of iron overload than the marrow iron stain. However, in addition to storage iron the marrow iron stain provides information about the effective delivery of iron to developing erythroblasts. Normally, 40 to 60% of developing erythroblastsѕcalled sideroblastsѕwill have visible ferritin granules in their cytoplasm. This represents iron in excess of that needed for hemoglobin synthesis. In states in which release of iron from storage sites is blocked, RE iron will be detectable, and there will be few or no sideroblasts. In the myelodysplastic syndromes, mitochondrial dysfunction occurs, and accumulation of iron in mitochondria appears in a necklace fashion around the nucleus of the erythroblast. Such cells are referred to as ringed sideroblasts.

 

 

 

Pict. 13 Bone marrow aspirate showing erythroid hyperplasia and many binucleated erythroid precursors.

 

 

 

Red Cell Protoporphyrin Levels. Protoporphyrin is an intermediate in the pathway to heme synthesis. Under conditions in which heme synthesis is impaired, protoporphyrin accumulates within the red cell. This can reflect an inadequate iron supply to erythroid precursors to support hemoglobin synthesis. Normal values are less than 30 ug/dL of red cells. In iron deficiency, values in excess of 100 ug/dL are seen. The most common causes of increased red cell protoporphyrin levels are absolute or relative iron deficiency and lead poisoning.

Serum Levels of Transferrin Receptor Protein. Because erythroid cells have the highest numbers of transferrin receptors on their surface of any cell in the body, and because transferrin receptor protein (TRP) is released by cells into the circulation, serum levels of TRP reflect the total erythroid marrow mass. Another condition in which TRP levels are elevated is absolute iron deficiency. Normal values are 4 to 9 ug/L determined by immunoassay. This laboratory test is becoming increasingly available and has been proposed to measure the serial expansion of the erythroid marrow in response to recombinant erythropoietin therapy.

 

 

 

Pict. 14. Microcytic anemia

 

 

 

Pict. 15. Peripheral smear showing classic spherocytes with loss of central pallor in the erythrocytes.

 

 

 

 

 

Pict. 16. Erythrocytes in severe iron deficiency.The large area of central pallor (anulocytes) is typical. The erythrocytes are flat, small, and appear pale

 

 

 

Pict. 17. Group of bone marrow erythroblasts in iron deficiency. The basophilic cytoplasm contrasts with the relatively mature nuclei (nuclear-cytoplasmic dissociation)

 

 

 

 

Pict. 18. In severe iron deficiency, even the cytoplasm of some mature erythroblasts is still basophilic and has indistinct margins

 

 

 

 

 

Pict. 19. Iron stain reveals absence of iron stores in bone marrow fragments due to severe iron deficiency

 

 

 

DIFFERENTIAL DIAGNOSIS

Other than iron deficiency, only three conditions need to be considered in the differential diagnosis of a hypochromic microcytic anemia.

 

 

 

 

TREATMENT

 

 

 

Pict. 20. Iron metabolism

 

 

The severity and cause of iron deficiency anemia will determine the appropriate approach to treatment. As an example, symptomatic elderly patients with severe iron deficiency anemia and cardiovascular instability may require red cell transfusions. Younger individuals who have compensated for their anemia can be treated more conservatively with iron replacement. The foremost issue for the latter patient is the precise identification of the cause of the iron deficiency.

For the majority of cases of iron deficiency (pregnant women, growing children and adolescents, patients with infrequent episodes of bleeding, and those with inadequate dietary intake of iron), oral iron therapy will suffice. For patients with unusual blood loss or malabsorption, specific diagnostic tests and appropriate therapy take priority. Once the diagnosis of iron deficiency anemia and its cause is made, and a therapeutic approach is charted, there are three major approaches.

Red Cell Transfusion  Transfusion therapy is reserved for those individuals who have symptoms of anemia, cardiovascular instability, and continued and excessive blood loss from whatever source, and those who require immediate intervention. The management of these patients is less related to the iron deficiency than it is to the consequences of the severe anemia. Not only do transfusions correct the anemia acutely, but the transfused red cells provide a source of iron for reutilization, assuming they are not lost through continued bleeding. Transfusion therapy will stabilize the patient while other options are reviewed.

Oral Iron Therapy  In the patient with established iron deficiency anemia who is asymptomatic, treatment with oral iron is usually adequate. Multiple preparations are available ranging from simple iron salts to complex iron compounds designed for sustained release throughout the small intestine (Table 105-5). While the various preparations contain different amounts of iron, they are generally all absorbed well and are effective in treatment. Some come with other compounds designed to enhance iron absorption, such as citric acid. It is not clear whether the benefits of such compounds justify their costs. Typically, for iron replacement therapy up to 300 mg of elemental iron per day is given, usually as three or four iron tablets (each containing 50 to 65 mg elemental iron) given over the course of the day. Ideally, oral iron preparations should be taken on an empty stomach, since foods may inhibit iron absorption. Some patients with gastric disease or prior gastric surgery require special treatment with iron solutions, since the retention capacity of the stomach may be reduced. The retention capacity is necessary for dissolving the shell of the iron tablet before the release of iron. A dose of 200 to 300 mg of elemental iron per day should result in the absorption of up to 50 mg of iron per day. This supports a red cell production level of two to three times normal in an individual with a normally functioning marrow and appropriate erythropoietin stimulus. However, as the hemoglobin level rises, erythropoietin stimulation decreases, and the amount of iron absorbed is reduced. The goal of therapy in individuals with iron deficiency anemia is not only to repair the anemia, but also to provide stores of at least 1/2 to 1 g of iron. Sustained treatment for a period of 6 to 12 months after correction of the anemia will be necessary to achieve this.

 

 

Contents of iron in some widely spread preparations:

 

 

Of the complications of oral iron therapy, gastrointestinal distress is the most prominent and is seen in 15 to 20% of patients. For these patients, abdominal pain, nausea, vomiting, or constipation often lead to noncompliance. Although small doses of iron or iron preparations with delayed release may help somewhat, the gastrointestinal side effects are a major impediment to the effective treatment of a number of patients.

The response to iron therapy varies, depending upon the erythropoietin stimulus and the rate of absorption. Typically, the reticulocyte count should begin to increase within 4 to 7 days after initiation of therapy and peak at 11/2 weeks. The absence of a response may be due to poor adsorption, noncompliance (which is common), or a confounding diagnosis. If iron deficiency persists, it may be necessary to switch to parenteral iron therapy.

 

 

 

Pict. 21. In the presence of some anemias, the body increases production of red blood cells (RBCs), and sends these cells into the bloodstream before they are mature. These slightly immature cells are called reticulocytes, and are characterized by a network of filaments and granules. Reticulocytes normally make up 1% of the total RBC count, but may exceed levels of 4% when compensating for anemia.

 

Parenteral Iron Therapy  Intramuscular or intravenous iron can be given to patients who are unable to tolerate oral iron, whose needs are relatively acute, or who need iron on an ongoing basis, usually due to persistent gastrointestinal blood loss. Currently, the intravenous route is used routinely. Parenteral iron use has been rising rapidly in the last several years with the recognition that recombinant erythropoietin therapy induces a large demand for ironѕa demand that frequently cannot be met through the physiologic release of iron from RE sources. Concern has been raised about the safety of parenteral iron-particularly iron dextran. The serious adverse reaction rate to intravenous iron dextran is 0.7%. Fortunately, newer iron complexes are becoming available in the United States that are likely to have an even lower rate of adverse effects. The most recently approved preparation is intravenous iron gluconate (Ferrlecit).

There are two approaches to the use of parenteral iron: one is to administer the total dose of iron required to correct the hemoglobin deficit and provide the patient with at least 500 mg of iron stores; the second is to give repeated small doses of parenteral iron over a protracted period. The latter approach is common in dialysis centers, where it is not unusual for 100 mg of elemental iron to be given weekly for 10 weeks to augment the erythropoietic response to recombinant erythropoietin therapy. The amount of iron needed by an individual patient is calculated by the following formula: body weight (kg) x 2.3 x (15 - patient's hemoglobin, g/dL) + 500 or 1000 mg (for stores).

In administering intravenous iron, anaphylaxis is always a concern. Anaphylaxis is less common with the newer preparations. The factors that have correlated with a serious anaphylactic-like reaction include a history of multiple allergies or a prior allergic reaction to dextran (in the case of iron dextran). Generalized symptoms appearing several days after the infusion of a large dose of iron can include arthralgias, skin rash, and low-grade fever. This may be dose-related, but it does not preclude the further use of parenteral iron in the patient. To date, patients with sensitivity to iron dextran have been safely treated with iron gluconate. If a large dose of iron dextran is to be given (>100 mg) the iron preparation should be diluted in 5% dextrose in water or 0.9% NaCl solution. The iron solution can then be infused over a 60 to 90 min period (for larger doses) or at a rate convenient for the attending nurse or physician. While a test dose (25 mg) of parenteral iron is recommended, in reality a slow infusion of a larger dose of parenteral iron solution will afford the same kind of early warning as a separately injected test dose. Early in the infusion of iron, if chest pain, wheezing, a fall in blood pressure, or other systemic manifestations occur, the infusion of iron-whether as a large solution or a test dose-should be interrupted immediately.

 

5. Megaloblastic anemia.

5.1.            Bone marrow.

5.2.            Criteria for cobalamin deficiency anemia.

5.3.            Criteria for folic acid deficiency anemia.

5.4.            Differential diagnosis of the megaloblastic anemias.

5.5.            Treatment of the megaloblastic anemias.

The megaloblastic anemias are disorders caused by impaired DNA synthesis. Cells primarily affected are those having relatively rapid turnover, especially hematopoietic precursors and gastrointestinal epithelial cells. Cell division is sluggish, but cytoplasmic development progresses normally, so megaloblastic cells tend to be large, with an increased ratio of RNA to DNA. Megaloblastic erythroid progenitors tend to be destroyed in the marrow. Thus, marrow cellularity is often increased but production of red blood cells (RBC) is decreased, an abnormality termed ineffective erythropoiesis.

Most megaloblastic anemias are due to a deficiency of cobalamin (vitamin B12) and/or folic acid.

 

CLASSIFICATION OF MEGALOBLASTIC ANEMIAS. CAUSES

The cause of megaloblastic anemia varies in different parts of the world. In temperate zones, folate deficiency in alcoholics and pernicious anemia are the common types of megaloblastic anemias. In certain areas close to the equator, tropical sprue is endemic and an important cause of megaloblastic anemia, while in Scandinavia, infestations by the fish tapeworm, Diphyllobothrium latum, may be a cause.

The dietary intake of cobalamin is more than adequate for the body's requirements, except in true vegetarians and their breast-fed infants. Thus deficiency of cobalamin is almost always due to malabsorption. Malabsorption can occur at several levels. In contrast, the dietary intake of folic acid is marginal in many parts of the world. Furthermore, because the body's stores of folate are relatively low, folic acid deficiency can arise rather suddenly during periods of decreased dietary intake or increased metabolic demand. Finally, folic acid deficiency may be due to malabsorption. Often two or more of these factors coexist in a given patient.

Combined deficiencies of cobalamin and folic acid are not uncommon. Patients with tropical sprue are often deficient in both vitamins. The biochemical lesion that results in megaloblastic maturation of bone marrow cells also causes structural and functional abnormalities of the rapidly proliferating epithelial cells of the intestinal mucosa. Thus severe deficiency of one vitamin can lead to malabsorption of the other. Furthermore, as discussed above, a deficiency of cobalamin causes a secondary reduction in cellular folic acid.

Finally, megaloblastic anemias may occasionally be induced by factors unrelated to a vitamin deficiency. Most such cases are caused by one or more of the many drugs that interfere with DNA synthesis. Less commonly, megaloblastic maturation is encountered in certain acquired defects of hematopoietic stem cells. Rarest of all are specific congenital enzyme deficiencies.

The finding of significant macrocytosis [mean corpuscular volume (MCV) > 100 fL] suggests the presence of a megaloblastic anemia. Other causes of macrocytosis include hemolysis, liver disease, alcoholism, hypothyroidism, and aplastic anemia. If the macrocytosis is marked (MCV > 110 fL), the patient is much more likely to have a megaloblastic anemia. Macrocytosis is less marked with concurrent iron deficiency or thalassemia. The reticulocyte count is low, and the leukocyte and platelet count may also be decreased, particularly in severely anemic patients. The blood smear demonstrates marked anisocytosis and poikilocytosis, together with macroovalocytes, which are large, oval, fully hemoglobinized erythrocytes typical of megaloblastic anemias. There is some basophilic stippling, and an occasional nucleated RBC may be seen. In the white blood cell series, the neutrophils show hypersegmentation of the nucleus. This is such a characteristic finding that a single cell with a nucleus of six lobes or more should raise the immediate suspicion of a megaloblastic anemia. A rare myelocyte may also be seen. Bizarre, misshapen platelets are also observed. The reticulocyte index is low. The bone marrow is hypercellular with a decreased myeloid/erythroid ratio and abundant stainable iron. RBC precursors are abnormally large and have nuclei that appear much less mature than would be expected from the development of the cytoplasm (nuclear-cytoplasmic asynchrony). The nuclear chromatin is more dispersed than expected, and it condenses in a peculiar fenestrated pattern that is very characteristic of megaloblastic erythropoiesis. Abnormal mitoses may be seen. Granulocyte precursors are also affected, many being larger than normal, including giant bands and metamyelocytes. Megakaryocytes are decreased and show abnormal morphology.

 

 

 

 

Megaloblastic anemias are characterized by ineffective erythropoiesis. In a severely megaloblastic patient, as many as 90% of the RBC precursors may be destroyed before they are released into the bloodstream, compared with 10 to 15% in normal individuals. Enhanced intramedullary destruction of erythroblasts results in an increase in unconjugated bilirubin and lactic acid dehydrogenase (isoenzyme 1) in plasma. Abnormalities in iron kinetics also attest to the presence of ineffective erythropoiesis, with increased iron turnover but low incorporation of labeled iron into circulating RBCs.

In evaluating a patient with megaloblastic anemia, it is important to determine whether there is a specific vitamin deficiency by measuring serum cobalamin and folate levels. The normal range of cobalamin in serum is 200 to 900 pg/mL; values <100 pg/mL indicate clinically significant deficiency. Measurements of cobalamin bound to TC II would be a more physiologic measure of cobalamin status, but such assays are not yet routinely available. The normal serum concentration of folic acid ranges from 6 to 20 ng/mL; values Ј4 ng/mL are generally considered to be diagnostic of folate deficiency. Unlike serum cobalamin, serum folate levels may reflect recent alterations in dietary intake. Measurement of RBC folate level provides useful information because it is not subject to short-term fluctuations in folate intake and is better than serum folate as an index of folate stores.

Once cobalamin deficiency has been established, its pathogenesis can be delineated by means of a Schilling test. A patient is given radioactive cobalamin by mouth, followed shortly thereafter by an intramuscular injection of unlabeled cobalamin. The proportion of the administered radioactivity excreted in the urine during the next 24 h provides an accurate measure of absorption of cobalamin, assuming that a complete urine sample has been collected. Because cobalamin deficiency is almost always due to malabsorption (Table 107-1), this first stage of the Schilling test should be abnormal (i.e., small amounts of radioactivity in the urine). The patient is then given labeled cobalamin bound to IF. Absorption of the vitamin will now approach normal if the patient has pernicious anemia or some other type of IF deficiency. If cobalamin absorption is still decreased, the patient may have bacterial overgrowth (blind loop syndrome) or ileal disease (including an ileal absorptive defect secondary to the cobalamin deficiency itself). Cobalamin malabsorption due to bacterial overgrowth can frequently be corrected by the administration of antibiotics. The Schilling test can provide equally reliable information after the patient has had adequate therapy with parenteral cobalamin.

A normal Schilling test in a patient with documented cobalamin deficiency may indicate poor absorption of the vitamin when mixed with food. This can be established by repeating the Schilling test with radioactive cobalamin scrambled with an egg.

Serum methylmalonic acid and homocysteine levels are also useful in the diagnosis of megaloblastic anemias. Both are elevated in cobalamin deficiency, while elevated levels of homocysteine but not methylmalonic acid are seen in folate deficiency. These tests measure tissue vitamin stores and may demonstrate a deficiency even when the more traditional but less reliable folate and cobalamin levels are borderline or even normal. Patients (particularly older patients) without anemia and with normal serum cobalamin levels but elevated levels of serum methylmalonic acid may develop neuropsychiatric abnormalities. Treatment of patients with this "subtle" cobalamin deficiency will usually prevent further deterioration and may result in improvement.

 

Pict. 22 This image shows a large PMN with multiple discretely-identifiable nuclear lobes, usually seen in megaloblastic anemias. Normal PMN's have less than or equal to 5 lobes.

 

COBALAMIN DEFICIENCY

The clinical features of cobalamin deficiency involve the blood, the gastrointestinal tract, and the nervous system.

The hematologic manifestations are almost entirely the result of anemia, although very rarely purpura may appear, due to thrombocytopenia. Symptoms of anemia may include weakness, light-headedness, vertigo, and tinnitus, as well as palpitations, angina, and the symptoms of congestive failure. On physical examination, the patient with florid cobalamin deficiency is pale, with slightly icteric skin and eyes. Elevated bilirubin levels are related to high erythroid cell turnover in the marrow. The pulse is rapid, and the heart may be enlarged; auscultation will usually reveal a systolic flow murmur.

Bone marrow morphology is characteristically abnormal. Marked erythroid hyperplasia is present as a response to defective red blood cell production (ineffective erythropoiesis). Megaloblastic changes in the erythroid series include abnormally large cell size and asynchronous maturation of the nucleus and cytoplasm – ie, cytoplasmic maturation continues while impaired DNA synthesis causes retarded nuclear development. In the myeloid series, giant metamyelocytes are characteristically seen.

The gastrointestinal manifestations reflect the effect of cobalamin deficiency on the rapidly proliferating gastrointestinal epithelium. The patient sometimes complains of a sore tongue, which on inspection will be smooth and beefy red. Anorexia with moderate weight loss may also be evident, possibly accompanied by diarrhea and other gastrointestinal symptoms. These latter manifestations may be caused in part by megaloblastosis of the small intestinal epithelium, which results in malabsorption.

The neurologic manifestations often fail to remit fully on treatment. They begin pathologically with demyelination, followed by axonal degeneration and eventual neuronal death; the final stage, of course, is irreversible. Sites of involvement include peripheral nerves; the spinal cord, where the posterior and lateral columns undergo demyelination; and the cerebrum itself. Signs and symptoms include numbness and paresthesia in the extremities (the earliest neurologic manifestations), weakness, and ataxia. There may be sphincter disturbances. Reflexes may be diminished or increased. The Romberg and Babinski signs may be positive, and position and vibration senses are usually diminished. Disturbances of mentation will vary from mild irritability and forgetfulness to severe dementia or frank psychosis. It should be emphasized that neurologic disease may occur in a patient with a normal hematocrit and normal RBC indexes. Although it has many benefits, folate supplementation of food may increase the likelihood of neurologic presentations of cobalamin deficiency.

In the classic patient, in whom hematologic problems predominate, the blood and bone marrow show characteristic megaloblastic changes (described under "Diagnosis," below). The anemia may be very severeѕhematocrits of 15 to 20 are not infrequent-but is surprisingly well tolerated by the patient because it develops so slowly.

Defective Release of Cobalamin from Food. Cobalamin in food is tightly bound to enzymes in meat and is split from these enzymes by hydrochloric acid and pepsin in the stomach. People older than 70 years are commonly unable to release cobalamin from food sources but retain the ability to absorb crystalline B12, the form most commonly found in multivitamins. The exact incidence of the defect in cobalamin release from food has not been well defined; estimates vary from 10 to greater than 50% of those over age 70 years. Only a minority of these persons go on to develop frank cobalamin deficiency, but many have biochemical changes, including low levels of cobalamin bound to TC II and elevated homocysteine levels, that augur cobalamin deficiency (see below).

Similarly, patients on drugs that suppress gastric acid production, such as omeprazole, may also fail to release cobalamin from food.

 

 

Pict 23. This picture shows large, dense, oversized, red blood cells (RBCs) that are seen in megaloblastic anemia. Megaloblastic anemia can occur when there is a deficiency of vitamin B-12.

 

Pernicious Anemia  Pernicious anemia, considered the most common cause of cobalamin deficiency, is caused by the absence of IF, from either atrophy of the gastric mucosa or autoimmune destruction of parietal cells. It is most frequently seen in individuals of northern European descent and African Americans and is much less common in southern Europeans and Asians. Men and women are equally affected. It is a disease of the elderly, the average patient presenting near age 60; it is rare under age 30, although typical pernicious anemia can be seen in children under age 10 (juvenile pernicious anemia). Inherited conditions in which a histologically normal stomach secretes either an abnormal IF or none at all will induce cobalamin deficiency in infancy or early childhood.

The incidence of pernicious anemia is substantially increased in patients with other diseases thought to be of immunologic origin, including Graves' disease, myxedema, thyroiditis, idiopathic adrenocortical insufficiency, vitiligo, and hypoparathyroidism. Patients with pernicious anemia also have abnormal circulating antibodies related to their disease: 90% have antiparietal cell antibody, which is directed against the H+,K+-ATPase, while 60% have anti-IF antibody. Antiparietal cell antibody is also found in 50% of patients with gastric atrophy without pernicious anemia, as well as in 10 to 15% of an unselected patient population, but anti-IF antibody is usually absent from these patients. Relatives of patients with pernicious anemia have an increased incidence of the disease, and even clinically unaffected relatives may have anti-IF antibody in their serum. Finally, treatment with glucocorticoids may reverse the disease.

 

 

 

 

Pict. 24. Peripheral smear of blood in a patient with pernicious anemia. Macrocytes are observed and some of the red blood cells show ovalocytosis. A 6-lobed polymorphonuclear leucocyte is present.

 

 

The destruction of parietal cells in pernicious anemia is thought to be mediated by cytotoxic T cells. Pernicious anemia is unusually common in patients with agammaglobulinemia, suggesting that the cellular immune system plays a role in its pathogenesis. In contrast, Helicobacter pylori does not cause parietal cell destruction in pernicious anemia.

The most characteristic finding in pernicious anemia is gastric atrophy affecting the acid- and pepsin-secreting portion of the stomach; the antrum is spared. Other pathologic changes are secondary to the deficiency of cobalamin; these include megaloblastic alterations in the gastric and intestinal epithelium and the neurologic changes described above. The abnormalities in the gastric epithelium appear as cellular atypia in gastric cytology specimens, a finding that must be carefully distinguished from the cytologic abnormalities seen in gastric malignancy.

The clinical manifestations are primarily those of cobalamin deficiency, as described above. The disease is of insidious onset and progresses slowly. Laboratory examination will reveal hypergastrinemia and pentagastrin-fast achlorhydria as well as the hematologic and other laboratory abnormalities discussed under "Diagnosis."

Through appropriate replacement therapy, patients with pernicious anemia should experience complete and lifelong correction of all abnormalities that are due to cobalamin deficiency, except to the extent that irreversible changes in the nervous system may have occurred before treatment. These patients, however, are unusually subject to gastric polyps and have about twice the normal incidence of cancer of the stomach. Thus, patients should be followed with frequent stool guaiac examinations and endoscopy when indicated.

Postgastrectomy  Following total gastrectomy or extensive damage to gastric mucosa as, for example, by ingestion of corrosive agents, megaloblastic anemia will develop because the source of IF has been removed. In all such patients, the absorption of orally administered cobalamin is impaired. Megaloblastic anemia may also follow partial gastrectomy, but the incidence is lower than after total gastrectomy. The cause of cobalamin deficiency after partial gastrectomy is not clear; defective release of cobalamin from food and intestinal overgrowth of bacteria have been suggested, but response to antibiotics is not common.

Intestinal Organisms  Megaloblastic anemia may occur with intestinal stasis due to anatomic lesions (strictures, diverticula, anastomoses, "blind loops") or pseudoobstruction (diabetes mellitus, scleroderma, amyloid). This anemia is caused by colonization of the small intestine by large masses of bacteria that consume intestinal cobalamin before absorption. Steatorrhea may also be seen under these circumstances because bile salt metabolism is disturbed when the intestine is heavily colonized with bacteria. Hematologic responses have been observed after administration of oral antibiotics such as tetracycline and ampicillin. Megaloblastic anemia is seen in persons harboring the fish tapeworm, D. latum, due to competition by the worm for cobalamin. Destruction of the worm eliminates the problem.

Ileal Abnormalities  Cobalamin deficiency is common in tropical sprue, while it is an unusual complication of nontropical sprue (gluten-sensitive enteropathy; Chap. 286). Virtually any disorder that compromises the absorptive capacity of the distal ileum can result in cobalamin deficiency. Specific entities include regional enteritis, Whipple's disease, and tuberculosis. Segmental involvement of the distal ileum by disease can cause megaloblastic anemia without any other manifestations of intestinal malabsorption such as steatorrhea. Cobalamin malabsorption is also seen after ileal resection. The Zollinger-Ellison syndrome (intense gastric hyperacidity due to a gastrin-secreting tumor) may cause cobalamin malabsorption by acidifying the small intestine, retarding the transfer of the vitamin from R binder to IF and impairing the binding of the cobalamin-IF complex to the ileal receptors. Chronic pancreatitis may also cause cobalamin malabsorption by impairing the transfer of the vitamin from R binder to IF. This abnormality can be detected by tests of cobalamin absorption (see below, Schilling test), but it is invariably mild and never causes clinical cobalamin deficiency. Finally, there is a rare congenital disorder, Imerslund-Grasbeck disease, in which a selective defect in cobalamin absorption is accompanied by proteinuria. Affected individuals have a mutation in cubulin, a receptor that mediates intestinal absorption of the cobalamin-IF complex.

 

 

Pict. 25. Peripheral smear showing ovalocytes, macrocytes, and a hypersegmented polymorphonuclear leukocyte

 

 

FOLIC ACID DEFICIENCY

Since January, 1998, folic acid has been added to all enriched grain products by order of the U.S. Food and Drug Administration; accordingly, the incidence of folic acid deficiency has fallen markedly. Patients with folic acid deficiency are more often malnourished than those with cobalamin deficiency. The gastrointestinal manifestations are similar to but may be more widespread and more severe than those of pernicious anemia. Diarrhea is often present, and cheilosis and glossitis are also encountered. However, in contrast to cobalamin deficiency, neurologic abnormalities do not occur.

The hematologic manifestations of folic acid deficiency are the same as those of cobalamin deficiency. Folic acid deficiency can generally be attributed to one or more of the following factors: inadequate intake, increased demand, or malabsorption.

Inadequate Intake  Alcoholics may become folate deficient because their main source of caloric intake is alcoholic beverages. Distilled spirits are virtually devoid of folic acid, while beer and wine do not contain enough of the vitamin to satisfy the daily requirement. In addition, alcohol may interfere with folate metabolism. Narcotic addicts are also prone to become folate deficient because of malnutrition. Many indigent and elderly individuals who subsist primarily on canned foods or "tea and toast" and occasional teenagers whose diet consists of "junk food" develop folate deficiency. Food folate supplementation has made folate deficiency very rare.

Increased Demand  Tissues with a relatively high rate of cell division such as the bone marrow or gut mucosa have a large requirement for folate. Therefore, patients with chronic hemolytic anemias or other causes of very active erythropoiesis may become deficient. Pregnant women formerly were at risk to become deficient in folic acid because of the high demand of the developing fetus. Deficiency in the first weeks of pregnancy can cause neural tube defects in newborns. Often the pregnancy was not detected until the defect had developed; thus, provision of folate supplementation to women after they learned they were pregnant was ineffective. However, folate food supplementation has decreased neural tube defects by more than 50%. Folate deficiency may also occur during the growth spurts of infancy and adolescence. Patients on chronic hemodialysis may require supplementary folate to replace that lost in the dialysate.

Malabsorption  Folic acid deficiency is a common accompaniment of tropical sprue. Both the gastrointestinal symptoms and malabsorption are improved by the administration of either folic acid or antibiotics by mouth. Patients with nontropical sprue (gluten-sensitive enteropathy) may also develop significant folic acid deficiency that parallels other parameters of malabsorption. Similarly, folate deficiency in alcoholics may be due in part to malabsorption. In addition, other primary small-bowel disorders are sometimes associated with folate deficiency.

 

 

Pict. 26. Histologically, the megaloblastosis caused by folic acid deficiency cannot be differentiated from that observed with vitamin B-12 deficiency.

 

 

DIAGNOSIS

The finding of significant macrocytosis [mean corpuscular volume (MCV) > 100 fL] suggests the presence of a megaloblastic anemia. Other causes of macrocytosis include hemolysis, liver disease, alcoholism, hypothyroidism, and aplastic anemia. If the macrocytosis is marked (MCV > 110 fL), the patient is much more likely to have a megaloblastic anemia. Macrocytosis is less marked with concurrent iron deficiency or thalassemia. The reticulocyte count is low, and the leukocyte and platelet count may also be decreased, particularly in severely anemic patients. The blood smear demonstrates marked anisocytosis and poikilocytosis, together with macroovalocytes, which are large, oval, fully hemoglobinized erythrocytes typical of megaloblastic anemias. There is some basophilic stippling, and an occasional nucleated RBC may be seen. In the white blood cell series, the neutrophils show hypersegmentation of the nucleus. This is such a characteristic finding that a single cell with a nucleus of six lobes or more should raise the immediate suspicion of a megaloblastic anemia. A rare myelocyte may also be seen. Bizarre, misshapen platelets are also observed. The reticulocyte index is low. The bone marrow is hypercellular with a decreased myeloid/erythroid ratio and abundant stainable iron. RBC precursors are abnormally large and have nuclei that appear much less mature than would be expected from the development of the cytoplasm (nuclear-cytoplasmic asynchrony). The nuclear chromatin is more dispersed than expected, and it condenses in a peculiar fenestrated pattern that is very characteristic of megaloblastic erythropoiesis. Abnormal mitoses may be seen. Granulocyte precursors are also affected, many being larger than normal, including giant bands and metamyelocytes. Megakaryocytes are decreased and show abnormal morphology.

Megaloblastic anemias are characterized by ineffective erythropoiesis. In a severely megaloblastic patient, as many as 90% of the RBC precursors may be destroyed before they are released into the bloodstream, compared with 10 to 15% in normal individuals. Enhanced intramedullary destruction of erythroblasts results in an increase in unconjugated bilirubin and lactic acid dehydrogenase (isoenzyme 1) in plasma. Abnormalities in iron kinetics also attest to the presence of ineffective erythropoiesis, with increased iron turnover but low incorporation of labeled iron into circulating RBCs.

In evaluating a patient with megaloblastic anemia, it is important to determine whether there is a specific vitamin deficiency by measuring serum cobalamin and folate levels. The normal range of cobalamin in serum is 200 to 900 pg/mL; values <100 pg/mL indicate clinically significant deficiency. Measurements of cobalamin bound to TC II would be a more physiologic measure of cobalamin status, but such assays are not yet routinely available. The normal serum concentration of folic acid ranges from 6 to 20 ng/mL; values Ј4 ng/mL are generally considered to be diagnostic of folate deficiency. Unlike serum cobalamin, serum folate levels may reflect recent alterations in dietary intake. Measurement of RBC folate level provides useful information because it is not subject to short-term fluctuations in folate intake and is better than serum folate as an index of folate stores.

Once cobalamin deficiency has been established, its pathogenesis can be delineated by means of a Schilling test. A patient is given radioactive cobalamin by mouth, followed shortly thereafter by an intramuscular injection of unlabeled cobalamin. The proportion of the administered radioactivity excreted in the urine during the next 24 h provides an accurate measure of absorption of cobalamin, assuming that a complete urine sample has been collected. Because cobalamin deficiency is almost always due to malabsorption (Table 107-1), this first stage of the Schilling test should be abnormal (i.e., small amounts of radioactivity in the urine). The patient is then given labeled cobalamin bound to IF. Absorption of the vitamin will now approach normal if the patient has pernicious anemia or some other type of IF deficiency. If cobalamin absorption is still decreased, the patient may have bacterial overgrowth (blind loop syndrome) or ileal disease (including an ileal absorptive defect secondary to the cobalamin deficiency itself). Cobalamin malabsorption due to bacterial overgrowth can frequently be corrected by the administration of antibiotics. The Schilling test can provide equally reliable information after the patient has had adequate therapy with parenteral cobalamin.

A normal Schilling test in a patient with documented cobalamin deficiency may indicate poor absorption of the vitamin when mixed with food. This can be established by repeating the Schilling test with radioactive cobalamin scrambled with an egg.

Serum methylmalonic acid and homocysteine levels are also useful in the diagnosis of megaloblastic anemias. Both are elevated in cobalamin deficiency, while elevated levels of homocysteine but not methylmalonic acid are seen in folate deficiency. These tests measure tissue vitamin stores and may demonstrate a deficiency even when the more traditional but less reliable folate and cobalamin levels are borderline or even normal. Patients (particularly older patients) without anemia and with normal serum cobalamin levels but elevated levels of serum methylmalonic acid may develop neuropsychiatric abnormalities. Treatment of patients with this "subtle" cobalamin deficiency will usually prevent further deterioration and may result in improvement.

 

 

 

 

Pict 27. Bone marrow aspirate from a patient with untreated pernicious anemia. Megaloblastic maturation of erythroid precursors is shown. Two megaloblasts occupy the center of the slide with a megaloblastic normoblast above.

 

 

TREATMENT

Cobalamin Deficiency  Apart from specific therapy related to the underlying disorder (e.g., antibiotics for intestinal overgrowth with bacteria), the mainstay of treatment for cobalamin deficiency is replacement therapy. Because the defect is nearly always malabsorption, patients are generally given parenteral treatment, specifically in the form of intramuscular cyanocobalamin. Parenteral treatment begins with 1000 ug cobalamin per week for 8 weeks, followed by 1000 ug cyanocobalamin intramuscularly every month for the rest of the patient's life. However, cobalamin deficiency can also be managed very effectively by oral replacement therapy with 2 mg crystalline B12 per day.

The response to treatment is gratifying. Shortly after treatment is begun, and several days before a hematologic response is evident in the peripheral blood, the patient will experience an increase in strength and an improved sense of well-being. Marrow morphology begins to revert toward normal within a few hours after treatment is initiated. Reticulocytosis begins 4 to 5 days after therapy is started and peaks at about day 7 (Fig. 107-3), with subsequent remission of the anemia over the next several weeks. If a reticulocytosis does not occur, or if it is less brisk than expected from the level of the hematocrit, a search should be made for other factors contributing to the anemia (e.g., infection, coexisting iron and/or folate deficiency, or hypothyroidism). Hypokalemia and salt retention may occur early in the course of therapy. Thrombocytosis may also be seen.

In most cases, replacement therapy is all that is needed for the treatment of cobalamin deficiency. Occasionally, however, a patient with a severe anemia will have such a precarious cardiovascular status that emergency transfusion is necessary. This must be done with great care, because such patients may develop heart failure from fluid overload. Blood must be administered slowly in the form of packed RBCs, with very close observation. A small volume of packed RBCs will frequently be enough to ameliorate the acute cardiovascular problems. If necessary, blood may be administered by exchanging patient blood (mostly plasma) for packed cells.

With lifelong treatment, patients should experience no further manifestations of cobalamin deficiency, although neurologic symptoms may not be fully corrected even by optimal therapy. The potential for late development of gastric carcinoma in pernicious anemia necessitates careful follow-up of the patient.

Folate, particularly in large doses, can correct the megaloblastic anemia of cobalamin deficiency without altering the neurologic abnormalities. The neurologic manifestations may even be aggravated by folate therapy. Cobalamin deficiency can thus be masked in patients who are taking large doses of folate. For this reason, a hematologic response to folate must never be used to rule out cobalamin deficiency in a given patient; cobalamin deficiency can be excluded only by appropriate laboratory evaluation.

In light of the high frequency of defective cobalamin absorption in older people and the possible increased risk that overt cobalamin deficiency will present with neurologic rather than hematologic symptoms (because of folate food fortification), some experts have recommended the use of 0.1 mg oral crystalline cobalamin prophylaxis daily in people over age 65 years.

 

 

 

 

Pict. 28. Response to therapy with cobalamin (Cbl) in a previously untreated patient with pernicious anemia. A reticulocytosis occurs within 5 days after an injection of 1000 mcg of Cbl. This lasts for about 2 weeks after injection. The hemoglobin (Hgb) concentration increases at a slower rate because many of the reticulocytes are abnormal and do not survive as mature erythrocytes.