Contributor: Gordon K. Klintworth
The term epidermolysis bullosa includes a heterogeneous group of inherited skin diseases that are characterized by the formation of vesicles at sites of minor trauma. The blisters in these diseases form at different levels in the epidermis and the conditions can be subdivided into four main categories based on the cleavage site in the epidermis: it may be within the epidermis [epidermolysis bullosa simplex], at the level of the hemidesmosomes [epidermolysis bullosa - hemidesmosomal], at the lamina lucida of the basement membrane zone [epidermolysis bullosa - junctional] or below the lamina densa of the basement membrane zone [epidermolysis bullosa - dystrophic]. At least 16 distinct forms of epidermolysis bullosa are recognized including localized epidermolysis bullosa simplex [epidermolysis bullosa simplex - localized],  generalized epidermolysis bullosa simplex [epidermolysis bullosa simplex - generalized],  epidermolysis bullosa letalis, generalized atrophic benign epidermolysis bullosa [epidermolysis bullosa - generalized atrophic benign], autosomal recessive dystrophic epidermolysis bullosa [epidermolysis bullosa - autosomal recessive dystrophic], autosomal dominant dystrophic epidermolysis bullosa [epidermolysis bullosa - autosomal dominant dystrophic]. Some forms of epidermolysis bullosa are associated with a progressive myopathy (including autosomal recessive epidermolysis bullosa) and have a mutation in the plectin gene. Some of these affected individuals have features of myasthenia gravis (ptosis, ophthalmoplegia and fatigable weakness). Several types of epidermolysis bullosa (dominant epidermolysis bullosa dystrophica, recessive epidermolysis bullosa dystrophica, pretibial epidermolysis bullosa dystrophica, epidermolysis bullosa with subcorneal cleavage, pretibial recessive epidermolysis bullosa dystrophica, recessive localista variant epidermolysis bullosa dystrophica, autosomal recessive epidermolysis bullosa prurinosa, autosomal dominant epidermolysis bullosa prurinosa) are due to mutations in the COL7A1 gene. Mutations in COL7A1 also cause abnormalities in the nails of the toes.