Disease overview

The dorsal hair ridge in Rhodesian and Thai Ridgeback dogs is caused by a mutation in fibroblast growth factor (FGF) genes, which predispose them to the congenital developmental disorder known as dermoid sinus. A dermoid sinus is a tubular indentation (like a tunnel) in the skin, above the spine, that can run deep into underlying tissues. These indentations can cause severe pain. While there are milder forms of dermoid sinus, category IV sinuses pose the greatest pain and risk, as they can connect with the spinal cord and cause life-threatening central nervous system infections.

Gene name

FGF4

Inheritance

Autosomal dominant

Signs and symptoms

Affected dogs will have an opening on the midline of the back. These are typically recognized at a young age. Some sinuses may not exhibit any clinical signs. Depending on the severity, affected dogs may present with discharge or signs of infection. If the sinus reaches the spinal cord, neurological abnormalities can be seen.

How is it diagnosed

A veterinarian will conduct a thorough exam, including a review of health history and any clinical signs. Radiographs with contrast may be indicated to observe the depth of the sinus. Genetic testing is necessary to determine if there is an underlying genetic cause, which can assist veterinarians with diagnosis and help breeders identify affected and carrier dogs.

Breeds at higher risk

Citations

Salmon Hillbertz NH, Isaksson M, Karlsson EK, Hellmén E, Pielberg GR, Savolainen P, Wade CM, von Euler H, Gustafson U, Hedhammar A, Nilsson M, Lindblad-Toh K, Andersson L, Andersson G. Duplication of FGF3, FGF4, FGF19 and ORAOV1 causes hair ridge and predisposition to dermoid sinus in Ridgeback dogs. Nat Genet. 2007 Nov;39(11):1318-20. doi: 10.1038/ng.2007.4. Epub 2007 Sep 30. PMID: 17906623.

Dickinson PJ, Bannasch DL. Current Understanding of the Genetics of Intervertebral Disc Degeneration. Front Vet Sci. 2020 Jul 24;7:431. doi: 10.3389/fvets.2020.00431. PMID: 32793650; PMCID: PMC7393939.

Waldo JT, Diaz KS. Development and validation of a diagnostic test for Ridge allele copy number in Rhodesian Ridgeback dogs. Canine Genet Epidemiol. 2015 Jan 27;2:2. doi: 10.1186/s40575-015-0013-x. PMID: 26401330; PMCID: PMC4579391.

Karlsson EK, Baranowska I, Wade CM, Salmon Hillbertz NH, Zody MC, Anderson N, Biagi TM, Patterson N, Pielberg GR, Kulbokas EJ 3rd, Comstock KE, Keller ET, Mesirov JP, von Euler H, Kämpe O, Hedhammar A, Lander ES, Andersson G, Andersson L, Lindblad-Toh K. Efficient mapping of mendelian traits in dogs through genome-wide association. Nat Genet. 2007 Nov;39(11):1321-8. doi: 10.1038/ng.2007.10. Epub 2007 Sep 30. PMID: 17906626.

Disclaimer

Disease diagnosis and treatment should always be performed by a veterinarian. The following information is for educational purposes only.