A point mutation,C to T,in exon 8 of the porphobilinogen deaminase gene in a Japanese family with acute intermittent porphyria

Summary Acute intermittent porphyria (AIP) is an autosomal dominant disease characterized by a deficiency of porphobilinogen deaminase (PBGD). To date, only two mutations have been reported in Japanese patients. We report here another mutation of the gene in a Japanese patient. Analysis of the PCR amplified DNA fragments of the gene by direct-sequencing method revealed the gene abnormality responsible for the disease. The mutation found was a point mutation, C to T, in exon 8 of the gene at position 346 of the housekeeping cDNA from the translation codon ATG. This mutation resulted in an Arg¹¹⁶ to Trp substitution. Four carriers in the family were successfully diagnosed by detecting the mutation using restriction analysis of PCR products.