G6PD and hyperinsulinemic hypoglycemia, familial, 4: Glucose-6-phosphate dehydrogenase (G6PD) deficiency is an inherited hemolytic disorder caused by a defect in the X chromosome, which is characterized by low G6PD enzyme levels in the red blood cells (RBCs) that produce nicotinamide adenine dinucleotide phosphate oxidase (NADPH) to protect the RBCs from oxidative injuries, preventing it from premature hemolysis [1].