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Hereditary spherocytosis is an inherited hemolytic anemia characterized by spherically shaped erythrocytes on the blood film, reticulocytosis, and splenomegaly. The principal cellular defect is the propensity to lose membrane surface area during passage through the splenic circulation, leading to spherical shape and decreased deformability. Splenic destruction of nondeformable spherocytes leads to anemia. Membrane loss results from defects in several membrane proteins, including ankyrin, band 3, α-spectrin, β-spectrin, and protein 4.2. Significant clinical, laboratory, biochemical, and genetic heterogeneity exists among patients with hereditary spherocytosis. Hereditary elliptocytosis is characterized by the presence of elliptical erythrocytes on the blood film, often with no or very slight shortening of red cell survival. The principal defect in the erythrocyte is a mechanical weakness caused by abnormalities in the proteins involved in the membrane skeleton, including α-spectrin, β-spectrin, protein 4.1, and glycophorin C. The majority of patients are asymptomatic, and therapy is rarely necessary. Hereditary pyropoikilocytosis is a rare cause of severe hemolytic anemia characterized by erythrocyte morphology similar to that seen in thermal burns. Acanthocytosis is characterized by the presence of contracted, dense erythrocytes with irregular projections on blood films, which may be seen in patients with severe liver disease, abetalipoproteinemia, after splenectomy, various neurologic disorders, and as a correlate of certain aberrant red cell antigens. Acanthocytes have abnormal red cell membrane lipid composition. The associated hemolysis is mild and rarely requires therapy. Stomatocytosis is a condition in which the red blood cells are principally composed of stomatocytes, red cells characterized by a central hemoglobin-free area shaped like a cigar or sausage or a very small circle. Stomatocytosis can be an inherited disorder or can occur in association with several acquired abnormalities. Stomatocytosis frequently is associated with abnormal red cell cation content, hydration, and membrane lipids. Great heterogeneity in the laboratory manifestations and clinical course of the stomatocytosis syndromes is observed. In some cases, abnormalities of band 3 and Rh-associated glycoproteins lead to altered membrane permeability.

Acronyms and Abbreviations

Acronyms and abbreviations that appear in this chapter include: αLELY, low-expression Lyon α-spectrin; αLEPRA, low-expression Prague α-spectrin; AQP1, aquaporin-1; ATP, adenosine triphosphate; BPG, bisphosphoglycerate; FP, familial pseudohyperkalemia; GPC, glycophorin C; GPD, glycophorin D; HAc, hereditary acanthocytosis; HE, hereditary elliptocytosis; HPP, hereditary pyropoikilocytosis; HS, hereditary spherocytosis; HSt, hereditary stomatocytosis; LCAT, lecithin-cholesterol acetyltransferase; MAGUK, membrane-associated guanylate kinase; MCHC, mean corpuscular hemoglobin concentration; MCV, mean corpuscular volume; PE, phosphatidylethanolamine; PI, phosphatidylinositol; PS, phosphatidylserine; RhAG, Rh-associated glycoprotein.

The erythrocyte membrane accounts for 1 percent of total weight of the red cell, yet it plays an integral role in the maintenance of erythrocyte integrity. The red cell membrane and its skeleton provide the erythrocyte the flexibility, durability, and tensile strength to undergo large deformations during repeated passages through narrow microcirculatory channels. The red cell membrane maintains a nonreactive exterior so that erythrocytes do not adhere to endothelial cells or aggregate and occlude the microcirculation. The membrane plays an important role in metabolism by selectively ...

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