UGT1A1 and Gerstmann syndrome: Crigler-Najjar syndrome (CNS) and Gilbert syndrome (GS) are inherited non-hemolytic unconjugated hyperbilirubinemias caused by mutations in the uridine diphosphate glucuronosyltransferase 1A1 (<i>UGT1A1</i>) gene, resulting in reduced or absent bilirubin conjugation.