PREMATURE TERMINATION CODONS ON BOTH ALLELES OF THE TYPE-VII COLLAGEN GENE (COL7A1) IN 3 BROTHERS WITH RECESSIVE DYSTROPHIC EPIDERMOLYSIS-BULLOSA

Epidermolysis bullosa (EB) is a group of heritable mechano-bullous skin diseases classified into three major categories on the basis of the level of tissue separation within the dermal-epidermal basement membrane zone. In the most severe, dystrophic (scarring) forms of EB, blisters form below the cutaneous basement membrane at the level of the anchoring fibrils, which are composed of type VII collagen, Ultrastructural observations of altered anchoring fibrils and genetic linkage to the type VII collagen locus (COL7A1) have implicated COL7A1 as the candidate gene in the dystrophic forms of EB. We have recently cloned the entire cDNA and the gene for human COL7A1. In this study, we describe distinct mutations in both COL7A1 alleles in three brothers with severe, mutilating recessive dystrophic EB (the Hallopeau-Siemens type, HS-RDEB). The patients are compound heterozygotes for two different mutations, both of which result in a premature termination codon in COL7A1, and the parents mere shown to be clinically heterozygous carriers of the respective mutations. Premature termination codons in both alleles of COL7A1 appear to be the underlying cause of severe, recessive dystrophic EB in this family.