American Society of Hematology (ASH) ITE Practice Test

Red blood cells rely on G6PD to generate NADPH, which keeps glutathione in its reduced form and protects the cells from oxidative damage. Variants differ in how active the enzyme is. The normal G6PD variant has full enzyme activity, so red cells withstand oxidative stress without undergoing hemolysis. In contrast, the Mediterranean, Canton, and Gaohe variants are deficient and render red cells more vulnerable to oxidative challenges (infections, certain drugs, or foods like fava beans), leading to hemolysis. So the variant with no hemolysis is the normal G6PD type.