EDA and hypohidrotic ectodermal dysplasia: Hypohidrotic ectodermal dysplasia (HED) is the one of the most common forms of ectodermal dysplasias (EDs), a group of disorders characterized by sparse hair, oligodontia, and reduced sweating.[1–3] It is caused by mutations in any of the ectodysplasin A (EDA) pathway genes.[4,5] Cui and Schlessinger[6] suggested that mutations in EDA, EDAR, or EDARADD genes are the causes of HED in humans.