Hyperkeratosis in Norfolk Terriers

Hyperkeratosis (HFH) is a skin disease characterized by excessive keratin production. It leads to cornification of the skin, particularly on the pads of the feet and the nose; it can also occur on the elbows and other parts of the body where it causes reddening of the skin, scaling and scabbing, which tend to be sites of entry for infection, cracking, bleeding and suppuration. The disease often arises in association with other health problems or an unbalanced diet, but in some breeds are predisposed to this disease. Clinical signs of the hereditary variant of the disease are evident in puppies as young as 4-5 months of age.

In the Norfolk Terriers, hyperkeratosis is caused by a missense mutation c.1125+1G>T in the KRT10 gene.

The mode of inheritance of the mutation is autosomal recessive. This means that only individuals who inherit the mutated gene from both parents will develop the disease. Carriers of the mutated gene are clinically healthy but pass the mutation on to their offspring. In the case of a mating between two heterozygous individuals, theoretically 25% of the offspring will be completely healthy, 50% of the offspring will be carriers and 25% of the offspring will inherit the mutated gene from both parents and will therefore be affected by the disease.

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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References:

Barnhart, KF., Credille, KM., Ambrus, A., Dunstan, RW. : Preservation of phenotype in an organotypic cell culture model of a recessive keratinization defect of Norfolk terrier dogs. Exp Dermatol 14:481-90, 2005. Pubmed reference: 15946235