Anhidrotic Ectodermal Dysplasia

Anhidrotic (hypohidrotic) ectodermal dysplasia is a hereditary X-linked recessive disorder which affects ectodermal structures. Hypohidrotic ectodermal dysplasia is one of about 150 types of ectodermal dysplasia in humans. Before birth, these disorders result in the abnormal development of structures including the skin, hair, nails, teeth, and sweat glands.

Most people with hypohidrotic ectodermal dysplasia have a reduced ability to sweat (hypohidrosis) 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. An 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.

Signs of Anhidrotic Ectodermal Dysplasia

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 absent teeth (hypodontia) 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.

Anhidrotic Ectodermal Dysplasia in Dogs

In dogs, a similar condition is called X-linked ectodermal dysplasia (XHED). There is a strong evidence that two conditions are caused by the same gene and, consequently, represent a single pathological disorder that affects both humans and dogs. This condition 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. Hair loss makes affected more dogs more susceptible to skin abrasions, cold and sunburn (and consequent skin cancer). The disorder has been reported in the German Shepherd dog.

Management of Anhidrotic Ectodermal Dysplasia

During hot weather, access to an adequate supply of water and a cool environment (spray bottle of water). Untreated XLHED dogs have an incomplete set of conically shaped teeth similar to those seen in human patients with XLHED. After treatment with EDA, significant normalization of adult teeth was achieved in four of five XLHED dogs. Moreover, treatment restored normal tear production and resistance to eye and airway infections and improved sweating ability. These results not only provide proof of concept for a potential treatment of this disease, but also demonstrate an essential role of EDA in the development of secondary dentition.

References

1. 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