Hair-nail dysplasia--a new pure autosomal dominant ectodermal dysplasia.

An apparently hitherto undescribed pure ectodermal dysplasia of the tricho-onychic subgroup is described. Its cause is an autosomal dominant gene with complete penetrance and variable expressivity. Differential diagnosis considered 18 conditions belonging to the same subgroup, as well as Clouston syndrome. This report increases the number of conditions of the tricho-onychic subgroup to 19, and the total number of ectodermal dysplasias to 155.