Test Detail

Group of genodermatoses characterised by painful keratotic thickening of the plantar pads of dogs, with fissures and crusts that limit walking. Within the common phenotype, at least two distinct molecular bases are recognised: in the Kromfohrländer, Irish Terrier (and Bedlington Terrier) the cause is a mutation in FAM83G (classic HFH), whereas in the Dogue de Bordeaux the cause is a mutation in KRT16 (focal non-epidermolytic palmoplantar keratoderma, FNEPPK1). In both forms the inheritance is autosomal recessive.

Affected breeds: Dogue de Bordeaux, Kromfohrländer, Irish Terrier (and Bedlington Terrier). In the Dogue de Bordeaux, the study of 334 dogs showed 245/306 clear and 61/306 carriers among the unaffected, suggesting a carrier frequency close to 20%. For the Kromfohrländer and Irish Terrier no large series with reliable allele frequency have been published; consider "limited data".

- Test breeding animals with the breed-specific test before mating: FAM83G c.155G>C for the Kromfohrländer and Irish Terrier; KRT16 indel for the Dogue de Bordeaux\n- Do not mate two carriers of the same variant: 25% risk of affected homozygotes\n- A carrier can be mated with a clear animal; the offspring intended for breeding must be tested and clear animals preferentially selected, progressively replacing the carrier without narrowing the gene pool\n- Exclude homozygous affected animals from breeding\n- In a dog with thickened and fissured pads, confirm the diagnosis with biopsy (orthokeratotic hyperkeratosis in HFH-FAM83G; in FNEPPK1-KRT16 conoidal "church spire" papillomatosis and parakeratotic hyperkeratosis) and, above all, with genetic testing\n- Do not spread the allele to lines where it is not present; remember that the FAM83G variant is shared by several related breeds

Differential diagnosis with other causes of digital hyperkeratosis: hereditary nasal parakeratosis of the Labrador due to SUV39H2 (also affects the nasal planum, not in HFH/FNEPPK1); epidermolytic ichthyosis of the Norfolk Terrier (affects generalised skin, not only the pads); digital hyperkeratosis due to leishmaniasis, pemphigus foliaceus, zinc-responsive dermatosis (Nordic breeds) or nutritional deficiency. Biopsy helps, but molecular testing is decisive. Remember that the Dogue de Bordeaux has its own molecular basis (KRT16) and will not benefit from a FAM83G test: always use the correct test for the breed. Palliative management with emollients, topical keratolytics (urea, salicylic acid) and early treatment of superinfections.

1. Drögemüller M, Jagannathan V, Becker D, Drögemüller C, Schelling C, Plassais J, Kaerle C, Dufaure de Citres C, Thomas A, Müller EJ, Welle MM, Roosje P, Leeb T. 2014. A mutation in the FAM83G gene in dogs with hereditary footpad hyperkeratosis (HFH) (PLoS Genet) (PMID 24832243).
2. Plassais J, Guaguère E, Lagoutte L, et al. 2015. A spontaneous KRT16 mutation in a dog breed: a model for human focal non-epidermolytic palmoplantar keratoderma (FNEPPK) (J Invest Dermatol) (PMID 25521457).
3. OMIA:001327-9615 (Hyperkeratosis, palmoplantar, FAM83G-related) y OMIA:002088-9615 (Palmoplantar keratoderma, nonepidermolytic, focal 1; KRT16).