X-linked hypohidrotic ectodermal dysplasia (XLHED; Christ–Siemens–Touraine syndrome; MIM #305100), the most frequent form of ED, is characterized by a symptom triad of hypotrichosis, hypo- or even anodontia, and hypo- or anhidrosis, caused by pathogenic variants of the gene EDA (MIM *300451) which encodes the signaling protein ectodysplasin A1. Here, EDA is linked to X-linked hypohidrotic ectodermal dysplasia.