Analysis of bilirubin UDP-glucuronosyltransferase gene mutations in an unusual Crigler-Najjar syndrome patient.

Crigler-Najjar (CN) syndrome is a rare autosomal recessive inherited disorder characterized by non-hemolytic, unconjugated hyperbilirubinemia. The levels of serum bilirubin and the response to phenobarbital treatment have been used to classify CN syndrome into two types: CN I and II. Mutations of the UGT1A1 gene have been found to be responsible for cases of CN syndrome. In the present study, the clinical features of a boy with an unusual type of CN syndrome were analysed. A DNA sample was obtained from the patient, and the promoter region, the exons and flanking intronic sequences of the UGT1A1 gene were analysed using the polymerase chain reaction and sequencing. The case was similar to CN type I in clinical features, but the therapeutic efficacy in the patient was superior to that typically observed in CN type II disease. Sequencing revealed compound heterozygous mutations, c.211G>A (p.G71R), c.1470C>T (p.D490D) and a normal homozygous A[TA]6TAA. No similar case has been reported worldwide and, considering the specific clinical features and therapeutic efficacy, a distinct type of CN was suspected. The phenotype of this unusual CN syndrome patient may be associated with the specific genotype.