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Keywords:

  • epidermolysis bullosa simplex;
  • genotype;
  • Japanese and Korean;
  • keratin 14;
  • keratin 5;
  • phenotype

Summary

Background  Epidermolysis bullosa simplex (EBS) comprises a group of hereditary bullous diseases characterized by intraepidermal blistering caused by mutations in either keratin gene, KRT5 or KRT14. Significant correlation between the position of mutations within these proteins and the clinical severity of EBS has been noted. A recent report showed EBS cases in Israel had unique genetic features compared with European or U.S.A. associated families, which suggests that the ethnic and geographical features of EBS patients may be different.

Objectives  To assess the possibility that EBS may present with certain specific features in Japanese and Koreans and to identify additional EBS mutations for genotype/phenotype correlation.

Methods  EBS was clinically diagnosed and confirmed by transmission electron microscopic examination of a skin biopsy. Mutation analysis of KRT5 and KRT14 was performed by direct sequencing in 17 Japanese and two Korean EBS patients.

Results  We have identified six novel KRT5 missense mutations (V143D, D158V, V186M, Q191P, R352S, G517D). R352S is the first mutation in the 2A domain. Most of these novel mutations changed amino acids that were evolutionarily conserved. Eight including all five mutations in EBS-Dowling–Meara patients have been previously reported. We were unable to detect mutations in five sporadic EBS-Koebner patients. The proportion of mutations in KRT5 (11 of 14; 78%) is higher than that for KRT14 mutations (3 of 14; 21%) in these Japanese and Korean EBS patients.

Conclusions  Japanese and Korean patients with EBS showed very similar phenotype and genotype correlations with patients from Western countries. Whether the higher proportion of KRT5 mutations is a definite characteristic of Japanese and Korean patients with EBS or not, requires further research into mutations in Japanese and Korean people.