Mutations affecting signalling through the cell surface receptor EDAR (OMIM#604095), either by mutation of EDAR itself or of the genes encoding its interaction partners EDA or EDARADD, cause hypohidrotic ectodermal dysplasia (also known as anhidrotic ectodermal dysplasia or Christ-Siemens-Touraine syndrome) [2]. The gene discussed is EDAR; the disease is X-linked hypohidrotic ectodermal dysplasia.