It has been demonstrated that HED is caused by mutations of several genes: ED1, encoding a ligand-ectodysplasinA-A1 (EDA-A1), EDAR, coding for ectodysplasinA-A1 receptor, EDARADD, programming the structure of EDAR-associated death domain protein and NEMO whose protein product, NFκB essential modulator (NEMO), is necessary for an indirect activation of nuclear factor κB (NFκB). This evidence concerns the gene EDAR and hypohidrotic ectodermal dysplasia.