The Ectodermal Dysplasias are a group of hereditary, non-progressive syndromes in which the affected tissue derives primarily from the ectodermal germ layer. The skin, its derivatives, and some other organs are involved. A predisposition to respiratory infections, due to a somewhat depressed immune system and to defective mucous glands in parts of the respiratory tract, is the most life threatening characteristic of this group of disorders.
Symptoms include eczema, poorly functioning sweat glands, sparse or absent hair follicles, abnormal hair, disfigured nails, and difficulties with the nasal passages and ear canals. Skin is satiny smooth, prone to rashes, and slow to heal. Commonly, the teeth fail to develop properly. Other complications may include hearing deficit, loss of sight, mental retardation, limb abnormalities, cleft palate and lip, and urinary tract anamolies. Allergies are common, as are bronchitis and pneumonia.
The numerous syndromes reported represent different combinations of these symptoms. They are traditionally grouped into the anhydrotic and hidrotic syndromes, according to whether they include the absence or severe deficiency of sweat glands. The syndrome have now been divided into three groups: pure, complex, and related. Pure ectodermal dysplasia syndrome involve only the hair, nails, sweat glands, and hair. Complex syndromes include these findings in addition to others. Syndromes in which other factors are primary to the effects on the hair, nails, sweat glands, or teeth are considered to be related conditions.
Some significant syndromes include Rapp-Hodgekin hypohidrotic ectodermal dysplasia, ectrodactyly ectodermal dysplasia, ectrodactyly-ectodermal dysplasia-clefting syndrome, trichorhinophalangeal syndrome, oral-facial-digital syndrome, nail dystrophy-deafness syndrome, trichodento-osseous syndrome, and the Johanson-Blizzard syndrome. (For more information on specific forms of Ectodermal Dysplasia, use the specific disease name as your search term in the Rare Disease Database.)
Ectodermal Dysplasias are a group of approximately 150 related diseases that result from faulty development of the ectodermal germ cell layer during embryogenesis. Because of the phenomenon of induction, derivatives of other cell layers may be affected. The exact genetic and biochemical defects are unknown, and are thought to vary from one form of the disorder to another.
The various syndromes have different inheritance patterns. Anhidrotic ectodermal dysplasia, for example, usually involves an X-linked recessive inheritance, with partial manifestation in females. However, it may also be transmitted as an autosomal dominant or recessive trait. X-linked recessive disorders are conditions that are coded on the X chromosome. Females have two X chromosomes, but males have one X chromosome and one Y chromosome. Therefore, in females, disease traits on the X chromosome can be masked by the normal gene on the other X chromosome. Since males only have one X chromosome, if they inherit a gene for a disease present on the X, it will be expressed. Men with X-linked disorders transmit the gene to all their daughters, who are carriers, but never to their sons. Women who are carriers of an X-linked disorder have a 50 percent risk of transmitting the carrier condition to their daughters, and a 50 percent risk of transmitting the disease to their sons. Syndromes with this pattern tend to be more severe.
The Rapp-Hodgkin Syndrome, by comparison, is an autosomal dominant disorder. In dominant disorders, a single copy of the disease gene (received from either the mother or father) will be expressed “dominating” the other normal gene and resulting in the appearance of the disease. The risk of transmitting the disorder from affected parent to offspring is 50 percent for each pregnancy regardless of the sex of the resulting child.
The gene for one form of Ectodermal Dysplasia known as Hypohidrotic Ectodermal Dysplasia (HED) has been located. Researchers plan to study the function of the gene and investigate the role of the proteins that are encoded by the H.E.D. gene. This gene identification will lead to a test for carrier status.
Ectodermal Dysplasias are a group of rare disorders that may affect males and females in equal numbers. It is estimated the approximately 125,000 individuals in the United States are carriers for some form of the disease.
No cure for the underlying causes of Ectodermal Dysplasia is known. Treatment is directed at symptoms. Over the counter creams may relieve skin discomfort. Dentures, hearing aids, etc. may be required. Heat and over- exercise are avoided. Vaccines and anti-infectious agents are used to reduce infections of skin and respiratory tract. Cleft palate and lip, syndactyly, and other limb deformations are treated by surgery.Precautions should be taken to minimize the effects of overheating while exercising or in warm temperatures.
Genetic counseling is important for Ectodermal Dysplasia patients and their relatives planning to have children.
Two research projects are underway to determine the gene responsible for Clouston Syndrome (Hidrotic Ectodermal Dysplasia). Participation in these projects involves a review of medical records and the donation of a small blood sample. A skin biopsy may also be requested. For more information, contact:
Amy Paller, M.D.
Division of Dermatology
Northwestern University Medical School
2300 Children’s Plaza
Jonathan Zonana, M.D.
Susan J Hayflick, M.D.
Oregon Health Sciences University
Department of Molecular and Medical Genetics
3181 SW Sam Jackson Park Road, L103
Portland, OR 97201-3098
Researchers are conducting a genetic study to investigate the relationship between Ectodermal Dysplasia and Split-Hand/Foot Deformity (ectrodactyly), which has been described as “EEC Syndrome” or Ectodermal Dysplasia, Ectrodactyly, and Clefting. The association among these syndromes may indicate a common gene or genes. For more information on this study, contact:
Bernard Weissman, M.D.
Philippa Charlton, M.D.
P.O. Box 7100
University of North Carolina
Chapel Hill, NC 27599-7100
The National Foundation for Ectodermal Dysplasias (NFED) and the School of Dental Medicine (SDM) at Southern Illinois University are engaged in a program to provide dental implants to individuals affected by Ectodermal Dysplasia. Interested individuals should contact NFED for the initial screening of potential participants. Such individuals must have Ectodermal Dysplasia, be missing a majority of teeth in the lower jaw (mandible), and not have any complicating factors. In addition, they must be willing to participate in the related research project, which requires periodic check-ups. For more information, please contact the National Foundation for Ectodermal Dysplasias, which is listed in the Resources section below.
Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government web site.
For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:
Tollfree: (800) 411-1222
TTY: (866) 411-1010
For information about clinical trials sponsored by private sources, contact:
Birth Defects Encyclopedia: Mary Louise Buyse, Editor-In-Chief; Blackwell Scientific Publications, 1990. Pp. 596-604.
The Merck Manual, 17th Ed.: Robert Berkow and Mark Beers, Editors; Merck Research Laboratories; 1999. P. 761.
Textbook of Dermatology, 5th Ed.: R.H. Champion, J.L. Burton, and F.J.G. Ebling, Editors; Blackwell Scientific Publications, 1992. Pp. 334-46, 376, 379, 1382, & 2694-95.
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eMedicine – Ectodermal Dysplasia: Article by Kara N Shah, MD, PhD
Hypohidrotic ectodermal dysplasia – Genetics Home Reference