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THE ERYTHROCYTE MEMBRANE

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  • The erythrocyte membrane plays a critical role in the maintenance of the biconcave shape and integrity of the red cell.

  • It provides flexibility, durability, and tensile strength, enabling erythrocytes to undergo extensive and repeated distortion during their passage through the microvasculature.

  • It consists of a lipid bilayer with embedded transmembrane proteins and an underlying membrane protein skeleton that is attached to the bilayer via linker proteins.

  • The integrity of the membrane relies on vertical interactions between the skeleton and the bilayer, as well as on horizontal interactions within the membrane skeletal network.

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ERYTHROCYTE MEMBRANE ABNORMALITIES

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  • Inherited membrane protein defects disrupt the membrane architecture and alter the shape of the cell resulting in hemolytic anemia as illustrated in Figure 13–1.

  • Protein defects that compromise vertical interactions between the membrane skeleton and the lipid bilayer result in destabilization of the bilayer, loss of membrane microvesicles, and spherocyte formation.

  • Protein defects affecting horizontal protein interactions within the membrane skeletal network disrupt the skeleton, resulting in defective shape recovery and elliptocytes.

  • Red cell membrane disorders exhibit significant heterogeneity in their clinical, morphologic, laboratory, and molecular characteristics.

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FIGURE 13–1

Blood films from patients with erythrocyte membrane disorders. A. Normal blood film. B. HS with dense spherocytes. C. SAO with large ovalocytes exhibiting a transverse ridge. D. HE with elongated elliptocytes and some poikilocytes. E. HSt with cup-shaped stomatocytes. F. Hereditary abetalipoproteinemia with acanthocytes. (Reproduced with permission from Lichtman’s Atlas of Hematology, www.accessmedicine.com.)

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Table 13–1 summarizes the relationship between red cell membrane proteins and disease phenotype.

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TABLE 13–1ERYTHROCYTE MEMBRANE PROTEIN DEFECTS IN INHERITED DISORDERS OF RED CELL SHAPE
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HEREDITARY SPHEROCYTOSIS

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Definition and Epidemiology

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  • Hereditary spherocytosis (HS) is characterized by osmotically fragile, spherical erythrocytes.

  • HS occurs in all race groups but is ...

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