CRIGLER-NAJJAR SYNDROME TYPE-II IS INHERITED BOTH AS A DOMINANT AND AS A RECESSIVE TRAIT

Crigler-Najjar syndrome type II (CN-II) is caused by a severely reduce d hepatic activity of bilirubin UDP-glucuronosyltransferase (UGT). Rec ently, by the analysis of the genetic background of CN-II patients, it has been clarified that the patients carry homozygous missense mutati ons or nonsense plus missense mutations on the gene for UGT, and CN-II was inherited as an autosomal recessive trait. We encountered a new c ase which had a nonsense mutation caused by a single nucleotide substi tution on one allele. This indicates that CN-II is also inherited as a dominant trait as well as a recessive trait. Expression study in vitr o strongly suggests that the disease in this case is caused by a domin ant negative mutation by forming a heterologous subunit structure.