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Cell Identification

VP

BS

-14

Participants

Identification No. % Evaluation

Spherocyte 885 97.3 Educational

Erythrocyte, normal 19 2.1 Educational

The arrows point to spherocytes, correctly identified by 97.3% of the participants. Spherocytes are

erythrocytes that are hyperchromic and lack central pallor due to their spherical shape. This contrasts

with normal erythrocytes, which have a biconcave shape and visible central pallor on smear preparations.

Spherocytes are often smaller than normal erythrocytes and may be very small (microspherocytes,

defined as <4 µm in diameter). Spherocytes form as a consequence of membrane loss, resulting in a

decreased ratio of cell surface membrane to cytoplasmic volume. Increased spherocytes are most

commonly seen in cases of immune hemolytic anemia and hereditary spherocytosis.

4

VP

BS

-15

Participants


Polychromatophilic RBC 887 97.7 Educational

Macrocyte oval/round 18 2.0 Educational

The arrowed cell is a polychromatophilic erythrocyte, correctly identified by 97.7% of the participants.

Polychromatophilic red cells are non-nucleated cells that are larger than normal erythrocytes, lack central

pallor, and have characteristic gray-blue cytoplasm. These cells correspond to reticulocytes, which can be

identified using supravital stains, and represent the final stage of red cell maturation. Normal blood

smears are expected to contain occasional polychromatophilic erythrocytes. Increased numbers indicate

that the bone marrow is actively working to increase red cell production, usually in response to bleeding or

hemolysis.

5

VP

BS

-16

Participants


Eosinophil 905 99.5 Educational

The arrowed cell is an eosinophil, correctly identified by 99.5% of the participants. Eosinophils are

leukocytes with characteristic bright, orange-red, refractile cytoplasmic granules of uniform size. The

granules typically do not overlie the nucleus. The nucleus usually contains two round to oval lobes of

equal size connected by a very thin filament.

6

VP

BS

-17

Participants


nRBC, normal/abnormal morphology 908 99.8 Educational

The arrowed cells are nucleated erythrocytes, correctly identified by 99.8% of the participants. Nucleated

erythrocytes seen in blood smears are typically at the orthochromic normoblast stage of maturation, which

is characterized by a round nucleus with markedly dense chromatin. Some nuclear irregularity may be

seen and does not necessarily indicate dyserythropoiesis, as the nucleus may develop an abnormal

shape as it migrates from the bone marrow into the blood. As seen in these examples, the cytoplasm of

circulating nucleated red cells typically displays polychromasia, and the cells are somewhat larger than

mature erythrocytes, reflecting their more immature maturation stage.

7

V

PB

S-1

8

Participants


Platelet, normal 907 99.7 Educational

The arrows point to normal platelets, correctly identified by 99.7% of the participants. Platelets are blue-

gray fragments of megakaryocytic cytoplasm that typically measure 1.5 to 3 µm in diameter and contain

fine, purple-red granules. Large platelets measure approximately 4 to 7 µm in diameter. The term “giant

platelet” is used when the platelet is larger than the size of an average red cell, assuming a normal MCV.

All of the platelets in this field demonstrate normal size and cytoplasmic granulation. No large or giant

platelets are seen.

8

VPBS-B 2012: Hereditary Spherocytosis

1- Education All material is © 2012 College of American Pathologists, all rights reserved.

Case History

The patient is a full-term, large for gestational age, baby boy with jaundice. There is a strong and extended

family history of spherocytosis on the father's side. Laboratory data include: WBC = 10.8 x 109/L; HGB =

7.6 g/dL; MCV = 90.8 fL; RDW = 23.3%; PLT = 849 x 109/L; Reticulocyte = 20.3%; Reticulocyte

Absolute = 537.8 K/UL; and elevated MCHC.

OVERVIEW OF HEMOLYTIC ANEMIA

Anemia is defined as a decrease in the number of red blood cells or decrease in blood hemoglobin

concentration that may result from a variety of causes such as red cell loss (eg, bleeding), decreased

production by the bone marrow, or increased destruction (eg, hemolytic). Case VPBS-B represents a patient

with hemolytic anemia secondary to hereditary spherocytosis (HS). Hemolytic anemia develops when the

survival of the red cells in the circulation is decreased from the normal life span of 110 to 120 days due to

their destruction within the circulation (intravascular hemolysis), by premature phagocytosis and

destruction by the spleen and reticuloendothelial system (extravascular hemolysis), or a combination of

both processes. Patients may have ongoing hemolysis without development of anemia (compensated

hemolysis) due to the ability of the bone marrow to increase the proliferation and differentiation of red cell

precursors by six- to eight-fold. However, when red cell life span is markedly shortened, usually to 15 to 20

days or less, the bone marrow is no longer able to adequately compensate for the red cell destruction. This

will lead to development of anemia as fewer red cells are produced than are destroyed. In addition, anemia

may develop in patients who have a longer red cell life span in situations where there is an acute

impairment of bone marrow function such as due to infection or drug exposure, leading to decreased red

cell production. An increase in red cell destruction due to activation of splenic function (usually due to viral

infection) may also lead to acute development of anemia in a patient with a hemolytic process that is

usually compensated.

CLASSIFICATION OF HEMOLYTIC ANEMIA

Hemolytic anemias may be subclassified in multiple ways, taking into account the various pathophysiologic

mechanisms underlying the anemia. It is often useful to think of the cause of red cell destruction when

investigating the etiology of hemolysis (Table 1). In this paradigm, anemia may be separated into either an

intrinsic or intracorpuscular defect of the red cell or hemolysis due to an extrinsic or extracorpuscular

process. An extracorpuscular defect implies that if the red cells were removed and transfused into another

patient they would have a normal life span, as the hemolysis is due to a process occurring within the

patient that is independent of the red cell (eg, thrombi that disrupt red cell integrity, hypersplenism).

Extracorpuscular hemolysis is usually an acquired disorder, and hemolysis will be decreased by treatment of

the underlying cause. In contrast, intracorpuscular hemolysis includes both acquired and inherited disorders

that directly affect red cell structure or essential functions. Affected red cells will have a shortened life

span even after being transfused into an unaffected patient due to the inherent abnormalities of the red

cell.



Many intrinsic hemolytic states are due to an inherited red blood cell defect, including hemoglobinopathies,

red cell membrane defects and enzymatic defects (Table 1). Thus, a good clinical history can provide a

great deal of insight into the underlying pathophysiology of the hemolysis, particularly if a family history is

identified, suggesting an inherited disorder. Examination of the peripheral blood smear is also an essential

component in evaluating hemolysis. Specific morphologic features, including identification of spherocytes,

poikilocytes, elliptocytes, stomatocytes, sickle cells, intraerythrocytic parasites, target cells, acanthocytes,

or prominent basophilic stippling can all provide clues as to the possible cause of hemolysis (Table 2). It is

important to utilize a well prepared blood smear that is free of artifacts to ensure optimal identification of

the specific red cell morphologic features.

Table 1 – Pathophysiologic Causes of Hemolysis

Intracorpuscular (intrinsic) causes of hemolysis:

Inherited defects

1. Red cell membrane defects a. Hereditary spherocytosis b. Pyropoikilocytosis

2. Enzymatic defects a. Glycolytic pathway defects – pyruvate kinase deficiency, etc.

3. Hemoglobinopathies a. Qualitative defects – sickle cell disease, hemoglobin C disease, hemoglobin E disease,

etc. b. Quantitative defects – thalassemias

Acquired defects

1. Paroxysmal nocturnal hemoglobinuria (PNH)

Extracorpuscular (extrinsic) causes of hemolysis:

1. Immune hemolytic anemias 2. Infections – malaria, etc. 3. Physical agents – burns, chemicals, toxins, etc. 4. Microangiopathic processes – disseminated intravascular coagulations (DIC), thrombotic

thrombocytopenia purpura (TTP), hemolytic uremic syndrome (HUS), etc. 5. Splenic sequestration/hypersplenism



Table 2 – Morphologic Features Associated with Specific Causes of Hemolysis

Spherocytes

Hereditary spherocytosis

Immune based hemolysis

Severe thermal injury or burn

Spider, bee, or snake venom

Clostridium septicemia

Poikilocytes

Microangiopathic and macroangiopathic anemias

Hereditary pyropoikilocytosis

Sickle Cells

Sickle cell anemia and other HbS hemoglobinopathies

Basophilic Stippling

Thalassemias

Lead poisoning

Pyrimidine 5’nucleosidase enzyme deficiency

Target Cells

Hemoglobinopathies (HbS, HbC, etc.)

Thalassemias

Acanthocytes

Uremia

Pyruvate kinase deficiency

Intracellular Parasites

Malaria

Babesiosis

Hb = hemoglobin



Another method of classification of hemolytic anemias is based on clinical presentation, such as separating

hemolytic anemias into inherited or hereditary causes versus those that are acquired (Table 1). Acquired

causes include most extrinsic processes as well as an uncommon acquired intrinsic defect in red cell

membrane proteins called paroxysmal nocturnal hemoglobinuria (PNH). This approach to classification is

often helpful in determining therapeutic approaches to hemolytic anemia but may also be useful in guiding

the workup of a hemolytic process.

LABORATORY FINDINGS INDICATIVE OF HEMOLYSIS

The laboratory approach to establishing a diagnosis of hemolysis depends on demonstrating sequelae of

increased red cell destruction. Often times, patients will not come to the attention of a physician until

anemia develops, and many patients with low level hemolysis will not be recognized until something

exacerbates the hemolysis or impairs the marrow’s ability to compensate for the shortened red cell life

span. This is typically manifested by increases in serum lactate dehydrogenase (LDH) and unconjugated

(indirect) bilirubin as well as decreased serum haptoglobin levels. Other tests that may be useful in

documenting hemolysis, primarily intravascular hemolysis, include detection of hemoglobinemia,

hemoglobinuria, and hemosiderinuria resulting from increased red cell breakdown.

Once hemolysis is identified, the first step in working up the cause of hemolysis is often performance of a

Coombs’ test (direct antiglobulin test) to identify anemias that arise due to immune-based hemolysis

(Coombs’ test positive) versus those that are not immune based (Coombs’ test negative). Because

hemolysis causes a decrease in red cell life span, the bone marrow will compensate by increasing

erythropoiesis. This will lead to erythroid hyperplasia in the marrow as well as early release of immature red

cells into the circulation. These immature red cells may be identified in the peripheral blood as reticulocytes

or nucleated red blood cells. Reticulocytes may be identified by supravital staining and are able to be

detected by many CBC analyzers as well as by manual methods. In peripheral blood smears, reticulocytes

are often macrocytic and demonstrate distinct blue to blue-gray coloration (polychromasia) that reflects the

presence of RNA, the Golgi complex and mitochondria within the immature red cell cytoplasm (Figure 1).

Enumeration of the number of reticulocytes as a percentage of all red cells yields the reticulocyte count.

Reticulocyte counts performed by manual methods using supravital stains have limited accuracy. In

contrast, CBC analyzers provide a very accurate reticulocyte count due to the higher number of red cells

sampled. The presence of nucleated red blood cells may also reflect premature release of erythrocytes into

the circulation in an attempt to compensate for anemia. Most often these will contain a condensed or

pyknotic nucleus (orthochromic normoblasts), but in cases of severe hemolysis earlier forms

(polychromatophilic or basophilic normoblasts) may be seen in the peripheral blood smear (Figure 2).



Figure 1. Polychromatophilic red cells. The three arrowed red cells show the characteristic larger size and blue-gray or basophilic color compared to the other erythrocytes in the image.

Figure 2. Nucleated red cells (orthochromic normoblasts). The two arrowed cells are circulating nucleated red cells that have small nuclei with condensed chromatin and pink to blue-gray cytoplasm.

SPHEROCYTES

The patient presented in case VPBS-B has a large number of spherocytes on the peripheral smear. A

spherocyte is defined as an abnormal red cell that is spherical, resulting in a greater density of hemoglobin

in the center of the red cell compared to a normal biconcave-shaped red cell that lacks central pallor.

Usually spherocytes are slightly smaller than normal red blood cells and occasionally they may be quite

small (microspherocytes) (Figure 3).

Figure 3. Spherocytes. The two arrowed red cells are spherocytes that appear smaller than the other red cells in the image and appear round with dense and homogenous cytoplasm that lacks central pallor.

Spherocytes occur due to loss of membrane from the red cell resulting in a decrease in the cell surface to

cytoplasmic ratio. To accommodate the loss in surface membrane in the setting of a constant cytoplasmic

volume the red cell is forced to assume a spherical shape. Spherocytes have a shortened life span in the



circulation because they lose the ability to deform as they pass through the spleen and small vessels of the

circulation and thus are lysed.

Spherocytes may be seen in a variety of different disease states (Table 3), and identification of spherocytes

in a blood smear mandates Coombs’ testing to rule out the possibility of an autoimmune or other antibody-

mediated hemolysis. HS is the most common cause of spherocytosis. Other causes of increased

spherocytes include septicemia with Clostridia species, severe burns or thermal injuries, as well as exposure

to venoms or severe hypophosphatemia. An appropriate clinical history should help to exclude those

differential diagnostic possibilities.

Table 3 –Conditions Associated with Increased Spherocytes

Common

Hereditary spherocytosis

Immune (warm antibody) based hemolysis

ABO incompatibility in neonates

Uncommon

Transfusion reaction hemolysis

Severe burns or thermal injury

Spider, bee, or snake venom

Clostridium sepsis

Acute red cell oxidation injury (glucose-6-phosphate dehydrogenase deficiency)

Severe hypophosphatemia

HEREDITARY SPHEROCYTOSIS

Overview of HS:

Hereditary spherocytosis (HS) is the most prevalent inherited cause of hemolytic anemia in patients of

Northern European ancestry and is usually the underlying etiology for increased spherocytes in the setting

of hemolysis when immune-based destruction is excluded. HS infrequently occurs in other ethnic groups. In

the United States, HS is seen in a frequency of approximately 1 out of 3,000 - 5,000. HS is typically

inherited as an autosomal dominant disorder, but other inheritance patterns may occur.

Red Cell Membrane Defects in HS:

Hereditary spherocytosis is a disorder of the red cell membrane. The normal red cell membrane is composed

of a lipid bilayer with an underlying protein cytoskeleton that acts to maintain the biconcave disk shape.



The biconcave shape allows for cellular deformability so that the red cell can pass undamaged through

small vessels and the splenic sinusoids as well as react to changes in pH, oxygen tension, and osmotic

gradients while in the circulation. The lipid bilayer is composed of phospholipids, cholesterol, and

glycolipids. These lipids arrange around the protein cytoskeleton, which contains a large number of proteins

that chemically interact to form a meshwork that allows for both vertical and horizontal interactions (Figure

4). The major proteins found in the red cell membrane skeleton include spectrin, actin, ankyrin, protein

4.1R, protein 4.2, and protein band 3 (also termed protein AE1). Spectrin is a principle component of the

membrane, comprising approximately 30% of the proteins in the red cell membrane. Spectrin is composed

of alpha and beta chains that interact to form long helical structures that support the biconcave shape of

the red cell and allow lateral or horizontal movement of the other cytoskeletal proteins. Spectrin binds

directly to ankyrin. In turn, ankyrin binds to protein band 3, and protein band 3 will bind to protein 4.2,

allowing for direct connection of the protein cytoskeleton to the lipid bilayer and vertical movement of the

protein cytoskeleton.

Figure 4. Schematic diagram of the red cell membrane. The figure shows a schematic representation of the interactions between the proteins of the red cell cytoskeleton and the lipid membrane demonstrating vertical and horizontal interactions.

Red cell membrane disorders result from alterations in either the binding qualities or the quantity of the

individual proteins within this red cell protein meshwork (Table 4). This leads to disruption of the typical

interactions between proteins and results in an uncoupling of the protein meshwork from the lipid bilayer

and normal binding of the integral membrane proteins to each other. This protein uncoupling results in

instability of the lipid bilayer so that it tends to form small vesicles or blebs that are subsequently removed

by the spleen. This cumulative membrane loss causes loss of the normal biconcave disc structure and

formation of spherocytes, as the decreased membrane is stretched to cover the constant volume of red cell

Horizontal Interactions

Band 3 (AE1)

Ve

rtic

al I

nte

rac

tio

ns



cytoplasm. Thus, the spleen plays a critical role in the development of hemolysis as it is responsible for

removal of the membrane microvesicles that lead to the formation of spherocytes as well as the

subsequent final destruction of the inflexible spherocytes.

Table 4 – Red Cell Membrane Protein Defects in Hereditary Spherocytosis

Protein Deficiencies

Ankyrin

Spectrin

Combined spectrin and ankyrin deficiencies

Band 3

Protein 4.2

Protein Dysfunction

β Spectrin to protein 4.1 binding

Band 3 binding to the lipid bilayer or ankyrin

Hereditary spherocytosis can be caused by abnormalities in several of the different components of the red

cell skeletal membrane including deficiencies in spectrin, ankyrin, band 3, and protein 4.2. Initially, spectrin

deficiency was thought to be the major underlying cause of HS; however, it has been found that in many

cases spectrin deficiency is due to qualitative or quantitative deficiencies of the other proteins which help

to integrate spectrin into the cell membrane leading to secondary loss of spectrin from the cell rather than

an inherited deficiency of spectrin production. For example, hereditary ankyrin defects (one of the most

common defects observed in HS) are often associated with a decreased amount of red cell spectrin due to

the lack of tethering of spectrin to the red cell protein meshwork, leading to loss of the protein. Studies of

red cell membrane protein synthesis and function in patients with hereditary spherocytosis have

demonstrated a variety of protein abnormalities including spectrin deficiency alone, combined spectrin and

ankyrin deficiency, band 3 deficiency, protein 4.2 deficiency, and some cases that have no obvious

biochemical abnormality but have protein dysfunction in that the proteins do not bind to each other or the

lipid membrane appropriately (Table 4). Each of these disease subsets is associated with specific mutations

that have specific ethnic associations, genetic findings and degrees of associated hemolysis (Table 5).

Although there are a wide variety of different proteins and molecular defects that underlie HS, the common

pathophysiologic defect appears to be the weakening of the protein-to-protein interactions and the resultant

lack of linkage of the lipid bilayer to the proteins of the cellular cytoskeleton in all cases.



Table 5 – Genetic Heterogeneity of Hereditary Spherocytosis

Genetic defect Hemolysis Inheritance pattern Frequency

Spectrin α-chain Severe Autosomal recessive Rare

Spectrin β-chain Mild to moderate Autosomal dominant Common, often associated with ankyrin deficiency ~20% of cases

Ankyrin deficiency Mild to severe Autosomal dominant Common ~60% of cases

Band 3 deficiency Mild to moderate Autosomal dominant Common ~20% of cases

Protein 4.1 deficiency Mild Autosomal dominant Rare, most common in North Africa

Protein 4.2 deficiency Moderate to severe (not responsive to splenectomy)

Autosomal recessive Rare, most common in Japan, rare in European population

Clinical Findings in HS:

Clinically, patients with HS often present with anemia, jaundice, and splenomegaly. However, the clinical

manifestations are highly variable and range from patients who have no anemia due to a relatively longer

red cell life span with bone marrow compensation to those who have severe hemolytic anemia due to a

very short red cell life span. The onset of symptoms is highly variable and many patients are not identified

until later in life when an infection or other process exacerbates the hemolysis or impairs the bone

marrow’s ability to compensate for more rapid red cell turnover (aplastic episode). The anemia seen in HS is

usually mild to moderate, but may be exacerbated with fatigue, cold exposure, pregnancy, or infection.

Often times, increased anemia is associated with increased jaundice due to increased red cell destruction

and hyperbilirubinemia. Some patients develop pigment (calcium bilirubinate) gallstones due to chronic

hemolysis.

Hereditary spherocytosis is clinically subclassified based on the severity of disease (Table 6). Most cases

are classified as moderate HS, which is a chronic hemolysis with characteristic spherocytes on the blood

smear, a negative Coombs’ test and a family history suggesting an autosomal dominant pattern of

inheritance. Mild disease is seen in 20 to 30% of patients. These patients will have no significant anemia

due to full compensation of hemolysis by the bone marrow. Usually splenomegaly is mild or absent and

patients are asymptomatic unless they have a hemolytic or aplastic episode that is triggered by an

infection. Moderate HS accounts for 60 to 75% of all cases. These patients will have mild to moderate



anemia, mild to moderate splenomegaly and intermittent jaundice. They will have increased reticulocyte

counts and bilirubin levels. Patients with moderate HS may require occasional transfusions. Moderately

severe to severe HS occurs in approximately 5% of cases and is characterized by significant hemolytic

anemia that may require multiple transfusions. Most cases of severe HS present during infancy and early

childhood and are more likely to be associated with an unusual nondominant pattern of inheritance.

Table 6 – Clinical Classification of Hereditary Spherocytosis

Mild HS Moderate HS

Moderately Severe HSa Severe HSb

Percent of cases 20-30% 60-75% 5% <10%

Hemoglobin (g/dL)

11-15 8-12 6-8 <6

Reticulocytes (%)

3-8 8 10 10

Bilirubin (mg/dL) 1-2 2 2-3 3

Peripheral smear Mild spherocytosis

Spherocytosis Spherocytosis Spherocytosis and poikilocytosis

Osmotic fragility fresh blood

Normal or slightly increased

Moderately increased

Moderately to severely increased

Severely increased

a Values in untransfused patients

b Patients with severe spherocytosis are always transfusion-dependent.

Laboratory Findings in HS:

The laboratory findings in most patients with HS include anemia, reticulocytosis, and an increased mean

corpuscular hemoglobin concentration (MCHC) with identification of spherocytes on the peripheral blood

smear (Table 7). There are usually normal numbers of white cells and platelets unless there is a

superimposed infection. Most patients will have increased bilirubin and LDH levels with decreased

haptoglobin. The anemia is typically mild to moderate and the MCV, despite the increased number of

spherocytes, may be normal due to the increased number of reticulocytes. There is varying amounts of

polychromasia and anisocytosis. The increase in MCHC is thought to be due to mild cellular dehydration

secondary to nonspecific loss of potassium through the membrane. The number of spherocytes may vary

considerably, and patients with severe hereditary spherocytosis also may have many poikilocytes.



Table 7 – Laboratory Features of Hereditary Spherocytosis

Blood

RBC

Variable normochromic, normocytic, or microcytic anemia (9-15 g/dL)

Variably increased reticulocytes

MCHC increased

Spherocytes present

WBC

Normal

Platelets

Normal

Bone Marrow

Variable cellularity (normocellular to hypercellular)

Variable erythroid hyperplasia

Laboratory

Evidence of hemolysis

Increased LDH

Elevated indirect bilirubin

Decreased haptoglobin

Specific Testing

Increased osmotic fragility

Decreased fluorescence intensity for eosin-maleimide by flow cytometry

LDH = lactate dehydrogenase; MCHC = mean corpuscular hemoglobin concentration; RBC = red blood cell; WBC = white blood cell



Additional testing for HS usually involves determination of red cell osmotic fragility. Spherocytes have

increased osmotic fragility due to the decrease in red cell membrane surface area relative to the volume of

cytoplasm. When red cells are placed in solutions that have differing salt concentrations, the ability of the

red cell to absorb water from solution is dependent on the ability to expand the red cell membrane. Thus,

the typical biconcave red cell is able to absorb more water from progressively more dilute salt

concentrations before lysis occurs compared to spherocytes. For spherocytes, the lower membrane to cell

surface ratio allows for less water to be absorbed from a hypotonic solution before lysis occurs. Osmotic

fragility testing is a good screening tool for hereditary spherocytosis but is not specific. Any patient with

increased numbers of spherocytes, including those with an immune-based hemolytic anemia, will show

increased osmotic fragility. Conversely, 10 to 20% of patients with hereditary spherocytosis, primarily

those with mild hereditary spherocytosis, will have normal to only slightly increased osmotic fragility.

A more specific test for diagnosis of hereditary spherocytosis can be done using flow cytometry.

Immunophenotypic detection of the levels of the band 3 (also referred to as AE1) protein and enumeration

by flow cytometry is a strong indicator of HS. The band 3 protein will bind the fluorescent dye eosin-

maleimide (EMA) at a protein site in one of the extramembrane domains. As band 3 is an essential

component of the red blood cell cytoskeleton, it will be decreased if there is a hereditary defect that impairs

the normal assembly of the protein framework. The level of EMA dye binding can be evaluated by flow

cytometry using the green fluorescent channel and gating on the red cell population. This test will detect

most cases of HS, as a defect in any of the cytoskeleton proteins (including spectrin and ankyrin) will lead

to a relative decrease in the levels of band 3 and a decreased fluorescent signal.

Use of clinical history, peripheral smear analysis to identify spherocytes, and in some cases the use of the

osmotic fragility and/or eosin-maleimide flow cytometry test are sufficient to allow a diagnosis of hereditary

spherocytosis in virtually all cases. In rare cases, additional testing by analysis of specific levels of each of

the red cell protein cytoskeletal components may be necessary; however, this is not a widely available test

and is usually not indicated.

Complications of HS:

Patients with long-standing HS are at risk for development of bilirubin gallstones. Patients also may have

episodes of worsening anemia that are due to physical stresses or infection that increase the rate of

hemolysis. This may be due to increased splenic activity (particularly in the case of viral infections) or due

to circulatory conditions that are more detrimental to the red cell, such as hypoxemia or changes in pH

(hemolytic crisis). Another complication that is usually due to infection with parvovirus B19 is an aplastic or

hypoplastic crisis in which the bone marrow’s ability to replace the hemolyzed red cells is markedly

impaired due to diminished erythropoiesis. Parvovirus infects red cell precursors and inhibits their growth,

resulting in a profound decrease in hemoglobin concentration and marked reticulocytopenia. Parvovirus

infection may be the initiating cause that brings a patient with HS to clinical attention due to the inability of

the bone marrow to compensate for hemolysis, even in mild to moderate cases of HS. Exaggeration of

anemia may also be seen with vitamin deficiencies, particularly deficiencies of folate due to pregnancy or



liver disease. These deficiencies act to inhibit compensatory increases in erythropoiesis within the bone

marrow, leading to an inability to produce sufficient numbers of red cells to compensate for hemolysis.

Clinical Management of HS:

As HS symptoms are dependent on the degree of hemolysis due to the alterations in red cell cytoskeletal

protein stability, each patient will have a unique clinical presentation. Most patients will have mild to

moderate hemolysis and a relatively benign clinical course. When hemolysis exceeds the ability of the bone

marrow to compensate, splenectomy may be performed and can greatly improve symptoms of anemia and

decrease the frequency of episodes of hemolysis associated with infection and other stresses. Red cell

transfusions are sometimes needed to treat intermittent increases in the severity of anemia during

hemolytic or aplastic crises.

REFERENCES:

1. Bolton-Maggs PHB, Stevens RF, Dodd NJ, et al. Guidelines for the diagnosis and management of

hereditary spherocytosis. Brit J Haematol. 2004;126:455-474.

2. Coetzer TL, Zail S. Introduction to Hemolytic Anemias. Intracorpuscular Defects: I. Hereditary Defects

of the Red Cell Membrane. In: Harmening DM, ed. Clinical Hematology and Fundamentals of

Hemostasis. 5th ed. Philadelphia, PA: F.A. Davis Company; 2009:176-195.

3. Gallagher PG, Glader B. Hereditary Spherocytosis, Hereditary Elliptocytosis, and Other Disorders

Associated with Abnormalities of the Erythrocyte Membrane. In: Greer JP, Forester J, Rodgers GM, et

al, eds. Wintrobe’s Clinical Hematology. 12th ed. Philadelphia, PA: Lippincott, Williams & Wilkins;

2009:911-930.

4. Glassy EF, ed. Color Atlas of Hematology: An Illustrated Field Guide Based on Proficiency Testing.

Northfield, IL: College of American Pathologists; 1998:100-103.

5. Grace RF, Lux SE. Disorders of the Red Cell Membrane. In: Orkin SH, Nathan DG, Ginsburg D, Look AT,

Fisher DE, Lux SE, eds. Nathan and Oski’s Hematology of Infancy and Childhood. 7th ed. Philadelphia,

PA: Saunders Elsevier; 2009:659-837.

6. Perkins, SL. Hereditary Erythrocyte Membrane Defects. In: Kjeldsberg CR, Perkins SL, eds. Practical

Diagnosis of Hematologic Disorders. 5th ed. Chicago, IL: ASCP Press; 2010:93-103.

Kyle T. Bradley, MD and Sherrie L. Perkins, MD Hematology and Clinical Microscopy Committee



AUTHOR’S BIO:

Kyle T. Bradley, MD, MS, FCAP is an assistant professor in the Department of Pathology and Laboratory

Medicine at Emory University Hospital in Atlanta, GA. He is board certified in anatomic pathology, clinical

pathology, and hematology by the American Board of Pathology. His primary responsibilities are in clinical

service and resident/fellow teaching in the areas of hematopathology and surgical pathology. Dr. Bradley

has authored a number of original articles, abstracts, and educational activities in the fields of

hematopathology and anatomic pathology and is a member of the College of American Pathologists (CAP)

Hematology and Clinical Microscopy Resource Committee.

Sherrie L. Perkins MD, PhD, FCAP is a professor of pathology at the University of Utah Health Sciences

Center and the chief medical officer for ARUP Laboratories in Salt Lake City, UT. She is the director of

hematopathology for ARUP Laboratories and has responsibilities in teaching, resident training, clinical

service, and research. Dr. Perkins has written more than 170 peer-reviewed papers and 70 book chapters

in the areas of hematology and hematopathology. Dr. Perkins is currently a member of the College of

American Pathologists (CAP) Hematology and Clinical Microscopy Resource Committee.

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