Background: We have screened 309,914 newborns in Yamagata prefecture, Japan, since 1977 and have detected four patients with phenylketonuria (PKU). We analyzed the phenylalanine hydroxylase (PAH) gene of the four patients to study the genetic background in this area and the genotype-phenotype relationship in these patients.
Methods: Mutations of the PAH gene were screened by denaturing gradient gel electrophoresis analysis and the sequences were determined.
Results: Three cases were compound heterozygotes of six different mutations of the PAH gene and the remaining case was a homozygote. Of the six detected mutations, K115fs is novel, whereas the others have been previously detected among Chinese and/or Japanese patients.
Conclusions: The incidence and genetic basis in Yamagata prefecture was similar to that of other parts of Japan. Analysis of the genotype is useful to understand the clinical variation in some families.