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Hereditary enzyme defect causes episodic hemolytic anemia from RBC's decreased ability to deal with oxidative stresses
Leads to excess oxidized glutathione that forces hemoglobin to denature and form precipitants called Heinz bodies
Heinz bodies cause RBC membrane damage, which leads to premature removal of these RBCs by reticuloendothelial cells within the spleen (extravascular hemolysis)
10–15% of American blacks have the variant G6PD isoenzyme designated A–, in which there is both a reduction in normal enzyme activity and a reduction in stability and therefore no hemolytic anemia
A– isoenzyme activity declines rapidly as the RBC ages past 40 days, a fact that explains the clinical findings in this disorder
Mediterranean variants have very low enzyme activity
Patients with G6PD deficiency seem to be protected from malaria parasitic infection, have less coronary artery disease, and possibly have fewer cancers and greater longevity
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Usually healthy, without chronic hemolytic anemia or splenomegaly
Hemolysis occurs at time of infection or exposure to certain drugs
Common drugs initiating hemolysis
Hemolytic episode self-limited, even with continued use of offending drug, because older RBCs (with low G6PD activity) removed and replaced with young RBCs (with adequate G6PD activity)
Chronic hemolytic anemia in severe G6PD deficiency (eg, Mediterranean variants)
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Blood is normal between hemolytic episodes
Hemoglobin rarely falls below 8 g/dL, reticulocytosis and increased indirect bilirubin during hemolytic episodes
G6PD enzyme assays low, especially in severe cases of G6PD deficiency
G6PD enzyme assays may be falsely normal if performed during or shortly after hemolytic episode during the period of reticulocytosis
Peripheral blood cell smear, although not diagnostic, may reveal bite cells and blister cells
Heinz bodies may be seen on peripheral blood smear with cresyl violet stain
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