UGT1A1 and Gerstmann syndrome: Serum bilirubin concentrations, the prevalence of benign hyperbilirubinemia > 17 μmol/L (1 mg/dL, a phenotypic sign of GS), and a variant of the UGT1A1 gene promoter responsible for GS manifestation in Caucasians (rs81753472) were evaluated in study subjects.