Gilbert’s Syndrome Revealed by Hepatotoxicity of Imatinib

Gilbert’s Syndrome (GS) is a hereditary disease that can cause hyperbilirubinemia due to a mutation in the promoter of the UGT1A1 gene, which causes a decrease in uridine diphosphate glucuronyltransferase enzyme activity. Polymorphisms in the UGT1A1 gene are associated with induced hyperbilirubinemia by Tyrosine Kinase Inhibitors (TKI) in Chronic Myeloid Leukemia (CML). We report a case of patient who developed hepatotoxicity when treated on Imatinib and subsequently diagnosed with Gilbert’s syndrome. Eight months after initiating Imatinib, the patient developed conjunctival jaundice and signs of hepatotoxicity with increase in liver enzymes and hyperbilirubinemia with elevated level of unconjugated bilirubin. Gilbert’s syndrome was suspected in the presence of predominantly unconjugated hyperbilirubinemia and a prior history of transient episodes of jaundice. Genetic testing revealed homozygosity for the UGT1A1 TA7 (*28) polymorphism. Imatinib was stopped due to continuous increase of aminotransferases and hyperbilirubinemia and restarted after improvement of Liver Function Tests (LFTs) with a reduced dose of 200 mg/day but LFTs worsted again, and the patient was switched to Dasatinib 100 mg/day, without hepatic cytolysis and a mild persistent hyperbilirubinemia after a follow up of 20 months. Patients with an unexplained rise in serum bilirubin levels on Imatinib therapy should be screened for the genetic UGT1A1 polymorphisms.