Epidermolytic Hyperkeratosis

Epidermolytic hyperkeratosis in dogs is a dermatological condition in which the dog's skin affecting keratin, a fibrous protein that forms the outer layer of the skin, resulting in fragile and scaly skin.

Symptoms

Symptoms are apparent within a few hours after birth, the skin is fragile, dry and flaking occurs, especially in areas of skin with folds or skin that rub together. In adults, dryness persists and dark gray hyperpigmentation occurs. Cracks and fissures in the skin occur and may bleed, so infections are common. Foot pads, claws, hair and teeth are normal.

Disease Management

It is important to note that the severity of symptoms may vary depending on the breed of dog and the stage of the disease. It is advisable to take your dog to the veterinarian if you detect any of these symptoms for proper diagnosis and treatment.

Genetic basis

This disease follows an autosomal recessive mode of inheritance. Autosomal recessive inheritance means that the dog, regardless of sex, must receive two copies of the mutation or pathogenic variant to be at risk of developing the disease. Both parents of an affected dog must carry at least one copy of the mutation. Animals with only one copy of the mutation are not at increased risk of developing the disease, but may pass the mutation on to future generations. Breeding between dogs carrying genetic variants that can cause disease, even if they do not show symptoms, is not recommended.

Technical report

Epidermolytic hyperkeratosis in dogs can be caused by mutations in several different genes that control keratin production in the skin such as KRT1, KRT10, LOR and FLG. KRT10 is a gene that provides instructions for making keratin 10. This protein is found in the skin and helps to maintain the structure and strength of skin cells. Mutations in the KRT10 gene can cause skin disorders such as epidermolytic hyperkeratosis, a condition in which the skin becomes thick and scaly. In the study by Credille et al. the c.1125+1G>T mutation (analyzed here) in the KRT10 gene was identified in a family of Norfolk Terrier dogs as causing a mild form of epidermolytic hyperkeratosis. The c.1125+1G>T variant affects a splicing site of the gene, which is important for proper processing of the KRT10 protein. Electron microscopy confirmed that affected dogs had decreased and clumping of tonofilaments, which are intermediate keratin filaments that help maintain the structure and strength of epithelial cells.

Most affected breeds

Norfolk Terrier

Bibliography

Credille KM, Barnhart KF, Minor JS,et al. Mild recessive epidermolytic hyperkeratosis associated with a novel keratin 10 donor splice-site mutation in a family of Norfolk terrier dogs. Br J Dermatol. 2005 Jul;153(1):51-8.