In humans, apart from the X-linked form of ectodermal dysplasia (XLHED) that involves mutation of the ectodysplasin gene ED1 (locus Xq12-q13.1), autosomal forms of the condition have also been described.35,36 These autosomal dominant and recessive forms of HED are linked to mutations of EDAR at the 2q11-q13 locus or EDARADD at the 1q42.2-43 locus. This evidence concerns the gene EDA and X-linked hypohidrotic ectodermal dysplasia.