G6PD

About G6PD

G6PD on chromosome Xq28 encodes glucose 6 phosphate dehydrogenase, the rate limiting enzyme of the pentose phosphate pathway, which produces NADPH. In red blood cells, which lack mitochondria, this pathway is the main source of NADPH, needed to keep glutathione in its reduced form and protect cells against oxidative damage. G6PD deficiency is the most common enzyme deficiency in humans, affecting an estimated 400 million people, particularly in Africa, the Mediterranean, the Middle East, and South and Southeast Asia, where it is thought to have been favored because it offers partial protection against malaria. Hundreds of variants are known, classified by the World Health Organization according to residual enzyme activity and clinical severity. Common variants such as the African A minus and Mediterranean variants usually cause no symptoms until an oxidative trigger produces acute hemolytic anemia. Triggers include fava beans, a reaction known as favism, infections, and certain drugs such as primaquine, tafenoquine, dapsone, rasburicase, and some sulfonamides, as well as naphthalene. Hemolysis causes jaundice, dark urine, fatigue, and back pain. Rare severe variants cause chronic hemolytic anemia. Deficiency is also a cause of neonatal jaundice. Because the gene is X linked, males are more often affected, though heterozygous females can be affected. G6PD testing is used before prescribing certain drugs.