Hypohidrotic Ectodermal Dysplasia
National Organization for Rare Disorders, Inc.
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Hypohidrotic ectodermal dysplasia (HED) is a rare inherited multisystem disorder that belongs to the group of diseases known as ectodermal dysplasias. Ectodermal dysplasias typically affect the hair, teeth, nails, and/or skin. HED is primarily characterized by partial or complete absence of certain sweat glands (eccrine glands), causing lack of or diminished sweating (anhidrosis or hypohidrosis), heat intolerance, and fever; abnormally sparse hair (hypotrichosis); and absence (hypodontia) and/or malformation of certain teeth. Many individuals with HED also have characteristic facial abnormalities including a prominent forehead, a sunken nasal bridge (so-called "saddle nose"), unusually thick lips, and/or a large chin. The skin on most of the body may be abnormally thin, dry, and soft with an abnormal lack of pigmentation (hypopigmentation). However, the skin around the eyes (periorbital) may be darkly pigmented (hyperpigmentation) and finely wrinkled, appearing prematurely aged. In many cases, affected infants and children may also exhibit underdevelopment (hypoplasia) or absence (aplasia) of mucous glands within the respiratory and gastrointestinal (GI) tracts and, in some cases, decreased function of certain components of the immune system (e.g., depressed lymphocyte function, cellular immune hypofunction), potentially causing an increased susceptibility to certain infections and/or allergic conditions. Many affected infants and children experience recurrent attacks of wheezing and breathlessness (asthma); respiratory infections; chronic inflammation of the nasal passages (atrophic rhinitis); scaling, itchy (pruritic) skin rashes (eczema); and/or other findings.
HED is usually inherited as an X-linked recessive genetic trait; in such cases, the disorder is fully expressed in males only. However, females who carry a single copy of the disease gene (heterozygote carreirs) may exhibit some of the symptoms and findings associated with the disorder. These may include absence and/or malformation of certain teeth, sparse hair, and/or reduced sweating. Researchers also have reported cases in which HED appears to be inherited as an autosomal recessive genetic trait. In such cases, the disorder is fully expressed in both males and females.
National Foundation for Ectodermal Dysplasias
410 East Main Street
PO Box 114
Mascoutah, IL 62258-0114
March of Dimes Birth Defects Foundation
1275 Mamaroneck Avenue
White Plains, NY 10605
NIH/National Arthritis and Musculoskeletal and Skin Diseases Information Clearinghouse
1 AMS Circle
Bethesda, MD 20892-3675
NIH/National Oral Health Information Clearinghouse
1 NOHIC Way
Bethesda, MD 20892-3500
Genetic and Rare Diseases (GARD) Information Center
PO Box 8126
Gaithersburg, MD 20898-8126
PO Box 241956
Los Angeles, CA 90024
Ectodermal Dysplasia Society
108 Charlton Lane
Glos, GL53 9EA
Tel: +44 (0) 1242 261332
Fax: +44 (0) 1242 261332
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