Mutations in EDA proteins ultimately lead to HED by blocking binding to the specific receptor[19,21,28] and inhibit the downstream NF-κB signaling pathway.[19] As the phenotypic penetrance of the mutations is very variable, further studies are necessary to show a more direct genotype–phenotype correlation for HED and to fully understand the mechanism of pathogenesis of HED. The gene discussed is EDA; the disease is hypohidrotic ectodermal dysplasia.