Dystrophic forms of epidermolysis bullosa.
Recent advances in the molecular genetics of the various forms of epidermolysis bullosa have disclosed the underlying genetic mutations in several different genes. In the dystrophic forms of EB, several lines of evidence indicate that type VII collagen gene is involved. First, the anchoring fibrils that consist of type VII collagen are altered, or they can be complete absent. Secondly, genetic linkage analyses using informative intragenic RFLPs in the type VII collagen gene and flanking polymorphic markers on the short arm of chromosome 3 have established linkage in families with the dystrophic forms of EB. Finally, discrete mutations in the type VII collagen gene have recently been disclosed in patients with the recessive dystrophic form of EB. These advances now provide the means for early prenatal diagnosis from chorionic villus biopsies during the first trimester of gestation, and will allow diagnosis by blastomere analysis before implantation in the future. Furthermore, understanding the precise mutations in the dystrophic forms of EB sets the stage for gene therapy to reverse the clinical phenotype in affected individuals.