The protein is a member of the tumor necrosis factor (TNF) receptor family, and is activated by its ligand EDA and uses EDARADD as an adaptor to build an intracellular NF-kB signal-transducing complex which is necessary for normal development of ectodermal organs both in humans and in mice [5,6], Autosomal dominant (AD) forms of HED have previously been linked to mutations in the ectodysplasin 1 anhidrotic receptor (EDAR) protein but mutations in the EDAR gene are also associated with recessive forms of ED [7,8]. Here, EDA is linked to hypohidrotic ectodermal dysplasia.