1998). UGT1A1*80, a synonymous variant often co‐inherited with UGT1A1*28 due to linkage disequilibrium, may also indirectly influence enzyme function. These variants are associated with mild hyperbilirubinemia and impaired irinotecan clearance. Of additional relevant is the missense variant p.G71R (UGT1A1*6), which is associated with decreased enzyme function. The gene discussed is UGT1A1; the disease is Hyperbilirubinemia.