Ectodermal Dysplasia (ED) is not a single disorder, but a group of closely related conditions. More than 150 different syndromes have been identified. The Ectodermal Dysplasias are heritable conditions in which there are abnormalities of two or more ectodermal structures such as the hair, teeth, nails, sweat glands, cranial-facial structure, digits and other parts of the body.