Hypohidrotic ectodermal dysplasia

**Definition:** Hypohidrotic ectodermal dysplasia is a genetic disorder of ectoderm development characterised by malformation of ectodermal structures such as skin, hair, teeth and sweat glands. It comprises three clinically almost indistinguishable subtypes with impaired sweating as the key symptom: Christ-Siemens-Touraine syndrome (X-linked), autosomal recessive and autosomal dominant hypohidrotic ectodermal dysplasia, as well as a fourth rare subtype with immunodeficiency as the key symptom.