Granulomatous sebaceous adenitis (GSA) is an idiopathic dermatosis of dogs and cats. GSA is characterized by cell mediated immunologic destruction of the sebaceous glands by T-lymphocytes and dendritic cells. The trigger for the disease is unknown, but a genetic cause is suspected, as studies have suggested an autosomal recessive mode of inheritance in poodles and Akitas. Abnormal lipid metabolism or keratinization defects are other theorized triggers for the disease.
GSA can affect any dog breed, although poodles, vizslas, Akitas, Havanese, Samoyeds and German Shepherd dogs are predisposed. Recently, I have seen this condition mainly in poodle mixes (Labradoodles and golden-doodles). I have not seen the condition recently in pure-bred poodles, likely because of a push amongst reputable poodle breeders to eliminate the disease from their breed.
The classic clinical sign is that of ‘follicular casts’. These are when a hair or group of hairs develop a collar of keratin debris around the base of the hair. Follicular casts can be seen with other dermatologic conditions, especially demodicosis, so follicular casts are not pathognomonic for GSA. Alopecia, scale, crust, matted hairs, and dull, brittle hairs can be seen as the condition progresses. In short coated dogs, the lesions often begin as areas of fine scaling and alopecia. The presence of follicular casting in short-coated dogs is variable. Staphylococcal pyoderma occurs commonly in dogs with GSA.
Differential diagnoses include Demodex overgrowth, staphylococcal pyoderma, dermatophytosis and keratinization defects. Biopsy is recommended as the definitive diagnostic tool, in addition to the other basic diagnostic tools to rule out other differential diagnoses.
Many different treatments have been advocated, but I focus on two main goals: stopping the immune destruction of the sebaceous glands and providing increased moisturization to replace the loss of oils from sebaceous gland destruction. To stop the cell-mediated destruction of the sebaceous glands I use cyclosporine (Atopica) at 5 mg/kg per day. Many animals can have the dose tapered eventually. When tapering, it is important to maintain each taper ‘step’ for several months, as it can take quite some time for clinical signs associated with a medication decrease to become evident. Steroids are not effective for GSA.
To moisturize the skin, a variety of products have been used including mineral oil soaks, 50% propylene glycol sprays, or various commercial products. I often use the Douxo Seborrhea or Chlorhexidine products and the Vetbiotek Hylagroom or Hexaderm shampoos because of their moisturizing qualities. I have owners use these products twice weekly. On non-bath days, I have owners apply a topical moisturizing product such as Douxo Seborrhea or Chlorhexidine spray or mousse.
Essential fatty acids or vitamin A may also be used, but these rarely make the difference between a well-controlled pet and a poorly-controlled pet in my experience.
In cats with GSA, Atopica is recommended as a first line therapy. Topical therapy as indicated above can be used if the animal is amenable to it. That said, most clients will just use Atopica!
Once treatment has started, it is important that clients have the correct set of expectations. Response can be slow, and can take several weeks to months to become evident. Even with appropriate therapy, many dogs will not regrow all of their hair, especially in cases where treatment was started relatively late in the progression of disease. In other words, if the disease progressed to the point that a hair follicle was destroyed, it will not come back. That said, treatment is still recommended as lack of treatment will result in progression of disease and frequent episodes of skin infection and discomfort.