Summary
Panniculitis is a term that describes inflammation of the fat-containing tissues just under the skin. An uncommon condition, it's been identified as a problem in dogs when bacteria, fungi or other organisms infect this area.
In it's rarer, sterile form (no infection present), it's been described as the result of a variety of diseases: pancreatitis, autoimmune diseases, cancers and vitamin E deficiency, among others. Drug reactions have also been implicated in this sterile form of panniculitis. The majority of sterile cases, however, are classified as "idiopathic," meaning we do not understand how the animal came to suffer this condition.
"Sterile nodular panniculitis" is the most commonly used term to describe this idiopathic disease process. It's thought to be the result of a disruption in normal blood flow through the fat layer that underlies the skin.
Symptoms and Identification
With sterile nodular panniculitis, single or multiple nodules of varying size and consistency will appear just under the skin. The head, neck, back and trunk are more commonly affected than other parts of the body. While unsightly, particularly when they eventually break open (fistulate) and drain a clear-ish fluid, they seem not to cause the animal any discomfort. Fever, inappetence and lethargy, however, may wax and wane along with the periodic appearance and resolution of the nodules.
Diagnosis is achieved with skin biopsies along with cultures to rule out infection. It's important, also, to evaluate the pet for any evidence of any recent drug administration or predisposing disease like pancreatitis or autoimmune conditions.
Affected Breeds
Dachshunds appear to be predisposed. Weimeraners have also been reported as affected. The mode of inheritance is unknown.
Treatment
Treating infection or underlying disease is paramount in non-idiopathic forms of the disease. In idiopathic forms, Vitamin E megadoses and other supplements have been administered with mixed results. Reports of treatment options include tetracycline, niacinamide, cyclosporine, prednisone and tacrolimus. With single lesions, surgical excision is considered an acceptable approach
Veterinary Cost
Because dermatologists will almost always be recommended to help diagnose and treat this rare condition, and because underlying diseases may necessitate long-term specialized care, the expense is likely to be quite high. Diagnosis would likely run at least $1,000-$2,000 depending on the degree of certainty required to rule out any underlying conditions. The cost of treatment would depend on the underlying cause, if any. Idiopathic cases' cost would depend on the drugs selected for treatment and whether any surgical options are elected.
Prevention
Because the hereditary nature of this disease is presumed, removing any affected dogs and their first degree relatives from the breeding pool is strongly recommended.
References
Alexander F. Koutinas, DVM, Dr. Vet. Med., DECVD; Professor M. Saridomichelakis, DVM, DrMedVet; The Skin As a Marker Of Internal Disease; Clinic of Internal Medicine, Faculty of Veterinary Medicine, Aristotle University of Thessaloniki.
Cross, J.R. et al. Bartonella-Associated Meningoradiculoneuritis and Dermatitis or Panniculitis in 3 dogs. Journal of Veterinary Internal Medicine. 2008; 22: 674-678.
Ackerman, LJ. Canine Nodular Panniculitis. The Compendium on Continuing Education Vol 6, No 9, September 1984, pp. 818-823.
Mellanby, RJ, et al. Panniculitis associated with pancreatitis in a cocker spaniel. Journal of Small Animal Practice 2003; 44: 24-28.
Kano, R, et al. Systemic Treatment of Sterile Panniculitis with Tacrolimus and Prednisolone in Dogs. Journal of Veterinary Medical Science 2005; 68(1): 95-96.