Dermoid Sinus in dogs

Dermatology: Dermoid Sinus (DS)

Dermoid sinuses are skin cavities of varying depths. These blind ended sacs often have openings on the skin surface.

Affected areas of the body:

Dogs can have single or multiple dermoid sinuses. They are normally found along the dorsal midline, caudal or cranial to the dorsal ridge in the cervical and lumbar areas, respectively.
However, contrary to popular opinion, dermoid sinuses do not appear below the dorsal ridge. Dermoid sinuses may also be present in the area of the skull.

Cause:

The disease is hereditary (incomplete separation of the neural tube and ectoderm), and it is present in affected dogs at birth, never developing at a later time.

Predisposition to dermoid sinus in Ridgeback breeds:

The hereditary transmission is not yet fully understood. Today, it is assumed to arise through an autosomal recessive inheritance pattern. It is known that "ridgeless" Ridgebacks also possess and can pass on the allele for DS. The ridge is the result of a genetic defect which presents an increased risk of dermoid sinus (Salmon Hillbertz & Anderson 2006, Salmon Hillbertz et al 2007).

Clinical symptoms:

Usually none. Complaints arise from inflammations/abscess formation or, in severe cases, from an inflammatory eruption. This can lead to neurological symptoms such as hyperaesthesia or the development of meningitis/myelitis.

Affected breeds:

Primarily Rhodesian Ridgebacks, but also other dog breeds. The incidence in Rhodesian Ridgebacks ranges from 3% to 20% of the population.

Diagnosis:

Targeted, thorough palpation of the skin from the crown to the croup (dermoid sinus palpable as strand-like structure between the thumb and index finger when pulling up on the skin folds. Shave area if necessary to reveal the skin opening and indentation).

Diagnostic confirmation:

Medical imaging (myelography, CT, MRI), especially pre-operatively and to determine the affected areas in the event of neurological symptoms. Additional CFS analysis if needed.

Therapy:

As soon as possible (puppy age), complete surgical excision of the entire dermoid sinus.

Alternative: If surgery is not desired, regular thorough (neurological) examinations.

Prognosis:

Favourable, neurological symptoms often reversible depending on severity, duration, and response to treatment. Dermoid sinus alone does not constitute reasonable grounds for euthanasia.

Affected dogs:

Animals with congenital abnormalities mustn´t be used for breeding (§11b of the German Animal Welfare Act (Tierschutzgesetz)

Concluding tip from DiploVets:

Predisposed breeds and their crossbreeds should be thoroughly checked during their first visit to the vet (for example for first vaccinations).


Bibliography: Upon request


Author of the article:

Veterinarian med. vet. Julia Brüner