Sebaceous adenitis is a skin disease of unknown pathogenesis; it may be immune-mediated, but this has not been proven. The disorder is inherited as an autosomal recessive trait in at least 2 breeds of dogs (poodles and akitas) and has been diagnosed in many other breeds. Clinically, the disease is characterized by silvery-white scales that adhere to the hair shafts and progresses to a dull, brittle hair coat and hair loss. Secondary bacterial and yeast infections are common. In vizslas, the disease presents with arciform and coalescing areas of alopecia. The diagnosis is made by skin biopsy. There is no specific treatment, and some dogs have responded to retinoids, presumably due to their antiinflammatory functions and effects on keratinocyte differentiation and sebaceous glands. Most treatment is palliative. Cyclosporine A has potent immuno-modulating effects and could be a treatment option. In this open study, 12 dogs with confirmed sebaceous adenitis were treated with 5 mg/kg PO Q 24 H for 1 year and were reevaluated every 4 months. A grading scale for clinical signs was devised and used to score lesions at each visit. Serum chemistry panels were monitored throughout the study, and the results were normal. Clinical lesions significantly decreased within 4 months of treatment and continued to decrease slightly throughout the 1-year treatment period. Skin biopsy specimens showed a decrease in inflammatory cells, and immunohistochemical staining showed a decrease in CD3+ T cells. Also, the percentage of hair follicles with increased sebaceous glands increased. At the beginning of the study, only 2% of hair follicles had sebaceous glands; after 4 months of therapy 32% did, and at the end of the study 40% did. Clinical signs returned when the drug was discontinued. Funded in part by Novartis Animal Health
COMMENTARY: Numerous anecdotal reports have noted that cyclosporine A is beneficial to dogs with sebaceous adenitis-this result was well documented in this study. Ten of 12 dogs responded to treatment; in the 2 that did not, therapy may have been ineffective because the disease was long-standing. The take-home messages from this study are that if a dog is going to benefit from therapy, it usually will do so within 4 months; cyclosporine A is well tolerated; and clinical signs recur after drug discontinuation. Because the disease is most common in large dogs, cost will be a factor for most clients. If the patient responds to therapy after 4 months, alternate-day therapy along with traditional topical emollient therapies may be a cost-effective alternative. In the study discussed here, no other therapy was allowed.
Effects of cyclosporine A on clinical and histologic abnormalities in dogs with sebaceous adenitis. Linek M, Boss C, Haemmerling R, et al. JAVMA 226:59-64, 2005.