OBJECTIVETo investigate the gene mutation in a Chinese pedigree and one sporadic case with pachyonychia congenita type I(PC-1), as well as to explore the relationship between the genotype and phenotype.

METHODSThe whole coding region of the KRT16 and KRT6A genes were amplified by long-range polymerase chain reaction (PCR). Six patients with PC-1 were studied, five of them were from a pedigree and the other one was sporadic. One unaffected member in the pedigree and 100 unrelated healthy individuals were also studied in order to exclude polymorphism. PCR products were directly sequenced to detect the mutation.

RESULTSNo mutations in the KRT16 gene were observed. All patients harbored a mutation in the KRT6A gene. All five patients in the pedigree had a mutation at codon 465 (TAC to CAC) which substitutes tyrosine (Y) by histidine (H). In the sporadic patient, codon 171 (AAC) was mutated to GAC, which changes the asparagines (N) to aspartic acid (D). No such mutations were found in the unaffected member of the pedigree and the 100 unrelated controls. The mutation of Y465H is located at the end of 2B and N171D at the beginning of 1A domain of KRT6A, both are hotspots for pathogenic keratin mutations.

CONCLUSIONThe mutations Y465H and N171D of the KRT16A gene were detected in the pedigree and the sporadic case respectively. The Y465H mutation was a novel mutation, and the N171D mutation was reported recently.