Hypohidrotic (anhidrotic) ectodermal dysplasia: molecular genetic research and its clinical applications.

X-linked hypohidrotic (anhidrotic) ectodermal dysplasia (EDA) results in abnormal morphogenesis of the teeth, hair, and eccrine sweat glands. The disorder is inherited as an X-linked recessive trait with significant morbidity and mortality in affected males, but with little to no clinical expression in many carrier females. Therefore, despite much effort, carrier detection based on clinical findings has been problematic. The locus for the disorder has now been localized to a region of less than one million base pairs on the X-chromosome, permitting DNA based carrier, prenatal, and early neonatal testing for many families. The isolation and sequencing of the EDA gene itself should be forthcoming by the application of the techniques of positional cloning. The isolation of the gene will allow direct mutation detection in even sporadic cases, and will further improve genetic counseling. It will also permit analysis of how the gene functions in the normal development of the epidermal and oral ectoderm, which may result in improved therapies for the disorder.