A homozygous mutation in UGT1A1 exon 5 may be responsible for persistent hyperbilirubinemia in a Japanese girl with Gilbert's syndrome.

The UGT1A1 gene encodes a responsible enzyme, UDP-glucuronosyltransferase1A1, for bilirubin metabolism. Many mutations have already been identified in patients with inherited disorders with hyperbilirubinemia, Crigler-Najjar syndrome and Gilbert's syndrome. In this study, we identified a UGT1A1 mutation in an 8-year-old Japanese girl with persistent hyperbilirubinemia who was clinically diagnosed as having Gilbert's syndrome. For the mutational analysis of UGT1A1, we performed a full sequence analysis of the gene using the patient's DNA. She was homozygous for a T to G transversion at nucleotide position 1456 in UGT1A1 exon 5 (c.1456T>G), leading to the substitution of aspartate for tyrosine at position 486 of the UGT1A1 protein (p.Y486D). In conclusion, the homozygous mutation of UGT1A1 may be responsible for persistent hyperbilirubinemia in this patient.