Multiplicity of mutation in UDP-glucuronosyltransferase 1∗1 gene in Gilbert's syndrome

Gilbert's syndrome is a constitutional mild unconjugated hyperbilirubinemia. In patients with this syndrome, mutation in the promoter and coding region of UDP-glucuronosyltransferase 1^∗1 gene have been reported independently. In the present study, we examined mutations in UGT1^∗1 gene using leukocytes of one male and four female patients with Gilbert's syndrome. In two cases, heterozygous mis-sense mutation of Gly71Arg was detected in exon 1A with simultaneous heterozygous mutation in the promoter region (2-base pair (TA)-insertion in the TATA box; A(TA)₇TAA, normal: A(TA)₆TAA). In the other three cases, mutation was not detected in the coding region and the homozygous A(TA)₇TAA mutation was observed. From these results, it is concluded that either homozygous mutation (inherited recessively) in TATA box of the promoter region or heterozygous mis-sense mutation (inherited dominantly) in the coding region were present in the patients with Gilbert's syndrome.