In total, four genes, namely ectodysplasin A (EDA), ectodysplasin A receptor (EDAR), EDAR-associated death domain protein (EDARADD) and Wnt family member 10A (WNT10A), are known to be involved in the etiology of HED.
Autosomal recessive (AR) forms of HED may be caused by pathogenic variants of the ectodysplasin A1 receptor (EDAR) gene that encodes a receptor involved in the NF-κB signaling pathway.
The EDA1R variant rs3827760 (p.Val370Ala), known to lessen HED-related symptoms, was found only in a single individual of Asian origin, but in none of the 123 European patients.
A founder ectodysplasin A receptor (EDAR) mutation results in a high frequency of the autosomal recessive form of hypohidrotic ectodermal dysplasia in India.
Significant differences in the number of some primary missing teeth (incisor and canine) related to EDA-EDAR genes defects were detected for the first time between XLHED and autosomal recessive HED, suggesting differential local effects of EDA-EDAR genes during odontogenesis.
Mutations in three functionally related genes EDA, EDAR and EDARDD have been reported to cause hypohidrotic ectodermal dysplasia (HED), which is characterized by sparse hair, reduced ability to sweat, and hypodontia.
The history and the lessons learned from hypohidrotic ectodermal dysplasia (HED) may serve as an example for the unraveling of the cause and pathogenesis of other ectodermal dysplasia syndromes by demonstrating that phenotypically identical syndromes (HED) can be caused by mutations in different genes (EDA, EDAR, EDARADD), that mutations in the same gene (EDA) can lead to different phenotypes (HED and selective tooth agenesis) and that mutations in genes further downstream in the same signaling pathway (NEMO) may modify the phenotype quite profoundly (incontinentia pigmenti (IP) and HED with immunodeficiency).
Thus, our study strengthens the role of this particular mutation in the aetiology of autosomal dominant HED and confirms the importance of EDAR for the development of HED.