Nevertheless, the ED1 mutation is not systematically identified in patients with HED: only 65.4% in a group of patients exhibiting the HED phenotype,39 other loci being mutated, such as EDAR (in 25% of non-ED1 HED) and, less often, EDARADD. 36,40. The gene discussed is EDA; the disease is hypohidrotic ectodermal dysplasia.