Hereditary Footpad Hyperkeratosis (FAM83G gene)

Hereditary hyperkeratosis of the plantar pads is a genetic disorder characterized by excessive growth and hardening of the outermost layer of the epidermis, known as the stratum corneum.

Symptoms

The disease manifests itself through clinical signs such as thickening and the formation of fissures and cracks on the surface of the pads, as well as the appearance of calluses on the edges. In addition, the nails may become tougher, deformed and grow at an accelerated rate. In some breeds such as the Kromfohrländer, coat changes such as loss of color and increased softness have been observed. Symptoms usually appear around 4-5 months of age.

Disease Management

Treatment of hereditary hyperkeratosis of the plantar pads focuses on options such as topical baths and ointments designed to soften and remove excess skin. It is important to consider the use of antibiotics to control secondary bacterial infections that may occur.

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

Hereditary hyperkeratosis of the plantar pads is a monogenic trait that is inherited in several breeds of dogs, such as Kromfohrländer and Irish Terriers. The gene related to the disease is FAM83G, although its exact function remains unknown. The study by Drögemüller M. et al. (2014) identified the nonsense c.155G>C variant, which involves the substitution of a G nucleotide for a C and the exchange of an evolutionarily conserved arginine for a proline residue. From these findings, it can be concluded that the FAM83G gene plays an essential role in maintaining the integrity of the palmoplantar epidermis.

Most affected breeds

Irish Terrier
Kromfohrländer

Bibliography

Drögemüller M, Jagannathan V, Becker Det al. A mutation in the FAM83G gene in dogs with hereditary footpad hyperkeratosis (HFH). PLoS Genet. 2014 May 15;10(5):e1004370.