Dermoid sinus (DS)

A dermoid sinus (DS) is a tube-like invagination of the skin. The invagination varies individually in depth of the tissue structure, sometimes as far as the spine, and can be targeted thorough palpation of the skin as a strand-like structure.
The dermoid sinus is filled with hair and sebum and causes no impairment to the dog as long as it does not become inflamed. However, if there is sudden inflammation, large abscesses and massive infections can occur. Normally, the dermoid sinus is found along the dorsal midline, less commonly in the cranial area.

The 10-year collaboration between Prof. Dr. Ottmar Distl (formerly TiHo Hannover), the DZRR and since last year also LABOKLIN has now enabled a genetic test for a risk factor for the development of dermoid sinus (DS) in Rhodesian Ridgeback. The genetic test was developed using genome-wide DNA sequence data and contains two genetic markers. These markers are located on two different chromosomes, allowing a total of nine different combinations of marker constellations.

Summary of the details:
1. Genetic test for DS: The test analyzes two genetic markers that are associated with an increased risk of DS.
2. Possible genotypes: There are different combinations of genes (e.g. AACC, TTCC, ATGG, etc.).
3. Risk assessment (as of February 2025) :

• AA-GG, AA-CG, AA-CC: Dogs with these genotypes have a very minimal (to zero) risk of developing DS.


• AT-GG, AT-CG: These dogs have a very low to low risk of DS.


• AT-CC, TT-GG: These dogs have a moderate risk of DS (about half the risk of TT-CC).


• TT-CG: These dogs have a higher risk of DS than the previous group.


• TT-CC: Dogs with this genotype have a very high risk of developing DS.

Importance for breeding:

• Goal: Avoid puppies with the high-risk genotype TTCC.


• Recommendation: Mating that could result in TTCC should be avoided.


• Tools: The table shows which matings (marked green) may not carry the risk genotype TTCC. In the matings shown in red, some or all of the puppies may carry the risk genotype.

Summary
The genetic test allows targeted breeding to minimize the risk of DS. Dogs, carrying genotypes with increased risk for DS, should not be mated with each other to further reduce the likelihood of puppies being born with DS.