Anhidrotic (hypohidrotic) ectodermal dysplasia is a hereditary X-linked recessive disorder which affects skin, lacrimal glands and teeth. It belongs to a group of disorders that are characterized by a number of congenital abnormalities which include sparse hair, inability to sweat, decreased tear production, frequent lung infections, and missing and malformed teeth. Most people with hypohidrotic ectodermal dysplasia have hypohidrosis (reduced ability to sweat) because they have fewer sweat glands than normal or their sweat glands do not function properly.
Sweating is a major way that the body controls its temperature; as sweat evaporates from the skin, it cools the body. Inability to sweat can lead to a dangerously high body temperature (hyperthermia), particularly in hot weather. In some cases, hyperthermia can cause life-threatening medical problems. Affected individuals tend to have sparse scalp and body hair (hypotrichosis). The hair is often light-colored, brittle, and slow-growing. This condition is also characterized by hypodontia (absent teeth) or teeth that are malformed. The teeth that are present are frequently small and pointed. Affected individuals also have decreased lacrimation (tear production) and frequent lung infections.
Ectodermal dysplasia has been described in pure and mixed-breed dogs, including the Miniature Poodle, Belgian Shepherd, Labrador Retriever, Bichon Frise, German Shepherd Dog, Whippet, Cocker Spaniel, and mixed breeds of the miniature pinscher and Pekingese.2 In dogs the condition is referred to as X-linked ectodermal dysplasia (XHED). There is a strong evidence that anhidrotic ectodermal dysplasia and XHED are caused by the same gene and, consequently, represent a single pathological disorder that affects both humans and dogs. XHED is seen from birth when the dogs are born with more than two thirds of their hair missing. Some dogs can develop the signs later in life. Most dogs with the condition lose all their hair when they get older. Alopecia makes affected dogs more susceptible to skin abrasions, cold, sunburn, and skin cancer.
Hypodontia and oligodontia are the most common dental manifestations of dogs affected with XLHED. The affected dogs may be missing multiple teeth, and some teeth are smaller than normal. Premolars are the most commonly absent teeth on both the upper and lower jaws. A mixed dentition of deciduous and permanent teeth is present beyond adolescence in 55% of adult XLHED-affected dogs.2 Normally, untreated XLHED dogs show decreased weight by age of two weeks when compared with their normal littermates. After treatment with Fc:EDA1 recombinant protein, significant normalization of adult teeth may be achieved in puppies. Moreover, treatment restores normal tear production and resistance to eye and airway infections and improves sweating ability.3
- Casal ML, Lewis JR, Mauldin EA, Tardivel A, Ingold K, Favre M, Paradies F, Demotz S, Gaide O, Schneider P. Significant correction of disease after postnatal administration of recombinant ectodysplasin A in canine X-linked ectodermal dysplasia. Am J Hum Genet
- JR Lewis,1 AM Reiter, EA Mauldin, and ML Casal. Dental abnormalities associated with X-linked hypohidrotic ectodermal dysplasia in dogs.
- Margret L. Casal, John R. Lewis, Elizabeth A. Mauldin, Aubry Tardivel, Karine Ingold, Manuel Favre, Fabrice Paradies, Stéphane Demotz, Olivier Gaide, and Pascal Schneider. Significant Correction of Disease after Postnatal Administration of Recombinant Ectodysplasin A in Canine X-Linked Ectodermal Dysplasia