Nail changes in epidermolysis bullosa: clinical and pathogenetic considerations.

Nail changes in epidermolysis bullosa (EB) are common, but although they are highly suggestive of the disease, they are not pathognomonic. They are the result of abnormalities of the nail matrix and nail bed, associated with the pathogenetic alterations of the dermo-epidermal junction which occur in EB. In addition, secondary trauma in the areas of epidermal-dermal separation, and chronic inflammation of the nail matrix, are probable contributory factors, even in non-scarring forms of EB. Recent developments in the molecular and cell biology of the cutaneous basement membrane zone have greatly advanced our understanding of the pathomechanisms underlying different subtypes of EB. Defects in genes coding for the structural proteins of the basement membrane zone have been defined in some EB subtypes, and abnormal expression of structural proteins in others. The data accumulated from study of these genetic disorders will contribute to knowledge of the role of the dermo-epidermal junction in the normal physiology and differentiation of the nails, and be of value in discerning the aetiopathogenesis of acquired nail diseases.