Ectodermal dysplasia

Ectodermal dysplasia is a group of inherited genetic disorders in which two or more structures that arise from the embryonic ectoderm develop or function abnormally. The affected structures include the hair, teeth, nails and sweat glands, and more than 200 distinct syndromes are classified under the name. The most common form is hypohidrotic ectodermal dysplasia, which affects roughly 1 in 5,000 to 10,000 live births and mainly affects males because it is inherited through the X chromosome. The cause lies in mutations in genes such as EDA, EDAR and EDARADD, which belong to signalling pathways, notably the EDA/NF-kappaB pathway, that guide ectodermal development in the embryo. Other forms follow autosomal dominant or autosomal recessive inheritance. Diagnosis rests on clinical examination for signs such as lack of sweating, characteristic dental and hair abnormalities and typical facial features, and genetic testing can confirm it, particularly when there is a family history.