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For further information, see CMDT Part 13-09: Hemolytic Anemias
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Generally classified according to whether the defect is intrinsic or extrinsic to the red blood cell (RBC)
Intrinsic defects have been described in all components of the red blood cell, including the membrane, enzyme systems, and hemoglobin; most of these disorders are hereditary
External factors are immune and microangiopathic hemolytic anemias and infections of red blood cells
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Serum haptoglobin may be low but is neither specific nor sensitive
Reticulocytosis present unless second disorder (infection, folate deficiency) superimposed on hemolysis
Transient hemoglobinemia occurs with intravascular hemolysis
Hemoglobinuria occurs when capacity for reabsorption of hemoglobin by renal tubular cells exceeded
Positive urine hemosiderin test indicates prior intravascular hemolysis
Hemoglobinemia and methemalbuminemia occur with severe intravascular hemolysis
Indirect bilirubin elevated, total bilirubin elevated to ≤ 4 mg/dL; higher bilirubin elevations may indicate hepatic dysfunction
Serum lactate dehydrogenase is elevated in microangiopathic hemolysis; may be elevated in other hemolytic anemias
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