UGT1A1 and Hyperbilirubinemia: However, the high prevalence of hemolytic disease such as G6PD deficiency, frequently exacerbated by (TA)n promoter polymorphism of the urine-diphosphate-glucuronosyltransferase 1A1 gene (UGT1A1) in this ethnic population mandates early detection and monitoring of infants with significant hyperbilirubinemia [16].