Glucose-6-Phosphate Dehydrogenase Deficiency

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

Usually healthy, without chronic hemolytic anemia or splenomegaly

Hemolysis occurs at time of infection or exposure to certain drugs

Common drugs initiating hemolysis

• Dapsone

• Methylene blue

• Phenazopyridine

• Primaquine

• Rasburicase

• Toluidine blue

• Nitrofurantoin

• Trimethoprim/sulfamethoxazole

• Sulfadiazine

• Pegloticase

• Quinolones

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)

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

Avoid known oxidant drugs

Otherwise, no treatment necessary