One patient, who had a persistent, mild, predominantly unconjugated hyperbilirubinemia preceding the initiation of antiviral treatment, was then diagnosed with a concomitant Gilbert syndrome, as confirmed by the homozygous polymorphism A(TA)7TAA in the promoter of the UDP-glucuronosyltransferase 1A1 gene. The gene discussed is UGT1A1; the disease is Gilbert syndrome.