Most common enzymatic disorder of RBCs. Causes extravascular and intravascular hemolysis.- X-linked recessive- African, Mediterranean, and Asian descent

Defect in G6PD → ↓ glutathion → RBC susceptibility to oxidant stress.Hemolytic anemia following oxidant stress (eg, sulfa drugs, antimalarials, infections, fava beans).

Findings:- Back pain- Hemoglobinuria a few days after oxidant stress.- Jaundice

Labs: blood smear shows RBCs with Heinz bodies and bite cells (degmacytes)