Defective UGT1A4 causes hyperbilirubinemia

UDP-glucuronosyltransferases (UGTs) play a major role in the conjugation and therefore elimination of potentially toxic xenobiotics and endogenous compounds. The 1-4 isoform UGT1A4 is able to act upon lipophilic bilirubin, the end product of heme breakdown. Defects in UGT1A4 can cause hyperbilirubinemia syndromes ranging from mild forms such as Gilbert syndrome (GILBS; MIM:143500) to the more severe Crigler-Najjar syndromes 1 and 2 (CN1, CN2; MIM:218800 and MIM:606785).

Summary from Reactome (R-HSA-5579016), read 2026-09-23.