ClinVar

In 2 affected sibs from a nonconsanguineous family with autosomal recessive hypohidrotic ectodermal dysplasia (ECTD10B; 224900), Monreal et al. (1999) detected a G-to-A transition at nucleotide 266 of the EDAR gene resulting in a nonconservative change of arg89 to his in the extracellular domain. The affected children were heterozygous at flanking polymorphic loci, but failed to inherit a paternal allele at the D2S1893 locus. Sequencing revealed their mother to be heterozygous for the variant, whereas their father was hemizygous wildtype. Thus, the affected individuals were compound heterozygotes, with their paternal allele containing a large deletion of indeterminate size (see 604095.0003).

Van der Hout et al. (2008) reported 2 brothers with hypohidrotic ectodermal dysplasia resulting from compound heterozygosity for the R89H and D110A (604095.0009) mutations in the EDAR gene. The unaffected father carried the D110A mutation. However, the mother, who was heterozygous for the R89H mutation, was mildly affected with hypohidrosis and few permanent teeth, consistent with autosomal dominant hypohidrotic ectodermal dysplasia (ECTD10A; 129490). Van der Hout et al. (2008) concluded that some presumably 'recessive' mutations may show phenotypic expression in carriers.