UGT1A1 and hyperinsulinemic hypoglycemia, familial, 4: Widespread glucose-6-phosphate dehydrogenase (G6PD) deficiency is also a principal predisposing factor to severe jaundice in Nigerian infants aggravated by (TA)n promoter polymorphism of the uridine-diphospate-glucuronosyltransferase 1A1 gene (UGT1A1)[25] and possibly the active promotion of exclusive breastfeeding[26].