Clinical Hematology and Fundamentals of Hemostasis

Abstract

Hemolytic anemias arise when red blood cells (RBCs) have decreased survival either due to an intrinsic abnormaLity of the cell or due to extrinsic factors or both. Intrinsic defects include genetic mutations causing. (1)hemoglobin disorders, either due to imbalance in the final product of α- and β-globin chains (quantitative disorders or thalassemias) or due to an abnormal globin chain synthesis (quaLitative disorders or hemoglobinopathies),(2)erythrocyte cytoskeleton disorders due to altered cytoskeleton mechanics and decreased erythrocyte deformabiLity,(3)deficiency of enzymes participating in the glycolytic and pentose phosphate pathway, leading to decreased RBC survival because of decreased energy production or increased oxidative damage in the erythrocytes.Extrinsic factors include the mechanical injury to erythrocytes in microangiopathic hemolytic anemia and immune-mediated conditions. An immune-mediated hemolytic anemia may be due to erythrocyte alloantibodies, most commonly in neonatal alloimmune hemolysis, or due to development of autoantibodies against the RBCs causing warm autoimmune hemolytic anemia, cold agglutinin syndrome, or paroxysmal cold hemoglobinuria.