We report here two unrelated families in Japan and Korea having patients with a unique type of epidermolysis bullosa simplex and a novel mutation in the keratin gene KRT5, i.e., a frameshift and delayed stop codon inconsistent with any subtype described before. The patients showed migratory circinate erythema and multiple vesicles on the circular belt-like areas affected by erythema. Electron microscopy of skin biopsies showed a reduction in the number of keratin intermediate filaments in the basal cells without tonofilament clumping. We identified a novel heterozygous deletion mutation (1649delG of KRT5) in both cases. This deletion is predicted to produce a mutant keratin 5 protein with a frameshift of its terminal 41 amino acids and 35 amino acids longer than the wild-type keratin 5 protein due to a delayed termination codon. As the same abnormal elongated mutant KRT5 gene was found in the independent families, the predicted abnormal elongated keratin protein is likely to lead to an atypical clinical phenotype that has never been reported, possibly by interfering with the functional interaction between keratin and its associated proteins.
Bibliographical noteFunding Information:
This work was supported by grants from the Scientific Research Fund of the Ministry of Education, Culture, Sports, Science, and Technology, Japan, and by grants from the Ministry of Health, Labor, and Welfare, Japan. The authors are indebted to Dr Walter Holleran, Dermatology Service, and University of California at San Francisco, for his extensive review and editing of this paper.
All Science Journal Classification (ASJC) codes
- Molecular Biology
- Cell Biology