Glucose-6-Phosphate Dehydrogenase (G6PD) Deficiency (G6PDD) is an inherited, sex-linked, metabolic disorder characterized by an enzyme defect that leads to the breakdown of red blood cells (hemolysis) upon exposure to stresses associated with some bacterial infections or certain drugs. A deficiency of this enzyme may result in the premature destruction of red blood cells (an acute hemolytic anemia).