Anhidrotic Ectodermal Dysplasia in German Shepherds

Ectodermal dysplasia is an inherited skin disease characterized by absent or abnormal teeth, impaired coat growth, missing sweat glands and reduced tear production. Puppies are born with symmetrical bald spots on the forehead and pelvic area, and often suffer from eye infections under closed eyelids. A major problem is the impaired mechanism for clearing matter from the respiratory tract, so-called mucociliary clearance (the ability to remove mucus by cilia), resulting in an increased susceptibility to pulmonary infections. Chronic nasal and ocular discharge or corneal ulceration is common.

The disease in German Shepherds is caused by a point mutation c.910-1G>A in the gene for ectodysplasin (EDA), which is necessary for the proper development of ectoderm derivatives - skin, coat, teeth and glands.

The mutation is X-linked. This means that it is localized on the X chromosome. Males have an X and a Y chromosome, so they can only be healthy (Xn/Y) or affected (Xm/Y). Females have two X chromosomes, so they can either be healthy (Xn/Xn), carriers (Xn/Xm) or affected (Xm/Xm). Female carriers do not show clinical signs but are able to pass the mutant allele to their offspring. Breeding of carrier females is not recommended. The genetic test can clearly reveal the genotype of the animal and is a useful tool for breeders to prevent unintentional breeding of affected puppies.

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Reference:

Casal, ML., Scheidt, JL., Rhodes, JL., Henthorn, PS., Werner, P. : Mutation identification in a canine model of X-linked ectodermal dysplasia. Mamm Genome 16:524-31, 2005. Pubmed reference: 16151697.