Ectodermal dysplasia (EDS) is a term including several conditions. All these conditions show differences in the formation of parts of the body derived from the ectoderm.
The ectoderm is one of three tissue layers found in very early embryonic development. It is involved in the formation of several parts of the body including the skin, hair, nails, teeth, mucous membranes, parts of the inner ear and the lens and retina of the eye. Dysplasia is a term which means something did not develop the way it should have.
For a condition to be called ectodermal dysplasia at least two parts of the body derived from the embryonic ectoderm need to have not developed in the normal way. There are over 150 types of ectodermal dysplasia. There are several different ways that ectodermal dysplasia can be inherited, X-linked, autosomal dominant and autosomal recessive. The inheritance pattern followed and the parts of the ectoderm affected will depend on which type of ectodermal dysplasia is involved.
What are the features of Ectodermal dysplasia?
The features associated with ectodermal dysplasia include:
- Thin hair
- Thin and/or small nails
- Cleft lip and/ or palate
- Problems with the function of sweat glands. If a person does not sweat enough or does not sweat at all, there is a danger of over heating. It is very important to ensure that this does not happen.
- Small or missing teeth
- More frequent respiratory infections than other family members without ectodermal dysplasia
- Hearing loss – The degree of hearing loss varies. If hearing loss is conductive (sound is not conducted from the external ear to the inner ear) it is often possible to improve it by surgery. However surgery is frequently unable to improve hearing if the hearing loss is sensorineural (the hearing problem is in the inner ear, auditory nerve or auditory centers of the brain). Hearing aids can help hearing in both types of hearing loss but if the loss is in the profound range, then hearing aids may only be able to help one hear general noise and not distinguish individual words.
- Vision problems – These vary depending on the type of ectodermal dysplasia present.
A person with ectodermal dysplasia will probably not have all of the problems listed above. Even within a family where more than one person has ectodermal dysplasia there may be variation of features and the extent to which they are shown.
The majority of people with ectodermal dysplasia are at no greater risk than the general population for learning problems, provided any visual or hearing problems that may be present are addressed.
Is there a test for Ectodermal dysplasia?
As may be expected with so many types of ectodermal dysplasia, there is not one change in one gene that leads to all the different types. Only a few types of ectodermal dysplasia have a known gene change. For most types of ectodermal dysplasia there is no testing. Even for the few types where a test is available, the results will not be able to tell exactly which features a person will have, and to what extent those features are affected.
- Online Mendelian Inheritance in Man, OMIM (TM). McKusick-Nathans Institute for Genetic Medicine, Johns Hopkins University (Baltimore, MD) and National Center for Biotechnology Information, National Library of Medicine (Bethesda, MD), 2000.