Dermoid sinus is a rare, genetic skin condition that affects dogs and cats. Since its symptoms resemble the pilonidal sinus in humans, this condition is also known as “pilonidal sinus”. However, compared to pilonidal sinus in humans, this condition is a neural tube defect. This type of sinus can appear as a single lump or a group of lumps on the dorsal midline. Common breeds affected with dermoid sinus include Kerry Blue Terriers, Boxers, Rhodesian Ridgeback and Shih Tzus.

Diagnosis is made by complete blood count, urinalysis, computed tomography scan, magnetic resonance imaging, myelogram and fistulogram, depending on the severity of the condition.

Some veterinarians administer folic acid in the bitch, one week before mating and until the first trimester of pregnancy. Some cases need surgery to remove abdominal tissues or close any connections to the spine. However, most cases of dermoid sinus lead to sinus regrowth.

Symptoms of dermoid sinus include fever, rigidity and spinal pain. Dermoid sinus could lead to myelitis and meningitis. Some cases can be extremely fatal.

Dermoid sinus is caused in the embryonic stage of development. Meaning, instead of spine development that separates from the skin, this separation does not take place in dogs or cats with dermoid sinus. As such, the sinus remains connected to the spinal cord.