EDAR and hypohidrotic ectodermal dysplasia: Nevertheless, both the identification of the R276C mutation in XL-HED patients and the defect it caused in the transcriptional reporter assay indicate that this mutation likely interferes with the in vivo interaction between EDA·A1 and EDAR and subsequent NF-κB activation, ultimately leading to the XL-HED phenotype (Figs. 4a, c and 5a, c).