Genetic studies of 20 Japanese families of dystrophic epidermolysis bullosa.

Dystrophic EB (DEB) is clinically characterized by mucocutaneous blistering in response to minor trauma, followed by scarring and nail dystrophy, and is caused by mutations in the COL7A1 gene encoding type VII collagen. DEB is inherited in either an autosomal dominant (DDEB) or recessive (RDEB) fashion. DDEB basically results from a glycine substitution mutation within the collagenous domain on one COL7A1 allele, while a combination of mutations such as premature stop codon, missense, and splice-site mutations on both alleles causes RDEB. In this study, mutation analysis was performed in 20 distinct Japanese DEB families (16 RDEB and four DDEB). The result demonstrated 30 pathogenic COL7A1 mutations with 16 novel mutations, which included four missense, five nonsense, one deletion, two insertion, one indel, and three splice-site mutations. We confirmed that Japanese COL7A1 mutations were basically family specific, although three mutations, 5818delC, 6573 + 1G > C, and E2857X, were recurrent based on previous reports. Furthermore, the Q2827X mutation found in two unrelated families would be regarded as a candidate recurrent Japanese COL7A1 mutation. The study furthers our understanding of both the clinical and allelic heterogeneity displayed in Japanese DEB patients.