Objective: To evaluate outcome of treatment with a combination of azathioprine and prednisone in dogs with meningoencephalomyelitis of undetermined etiology (MUE).
Design: Retrospective case series.
Animals: 40 dogs.
Procedures: Medical records of dogs with MUE treated with prednisone and azathioprine were evaluated with regard to response, survival, and adverse effects.
Results: All dogs improved during treatment. Twenty-four (60%) dogs had a complete response (resolution of clinical signs), and the other 16 (40%) dogs had a partial response (improvement but not resolution of signs). Most dogs that achieved a complete response remained neurologically normal. Six dogs remained stable after a partial response. Eleven dogs had a relapse of clinical signs. Twenty dogs died during the study period, 18 survived, and 2 were lost to follow-up monitoring. Median survival time was 1,834 days (range, 50 to 2,469 days). Survival time was significantly longer for dogs that had a complete response than for those that did not. Survival time was significantly shorter for dogs that relapsed than for those that did not. The most common adverse effects included weight gain, thinning of the hair, and elevated activities of liver enzymes, all of which may have been attributed to concurrent corticosteroid administration. Less common adverse effects included diabetes mellitus, keratoconjunctivitis sicca, mammary gland adenoma, lymphoma, and hepatic masses.
Conclusions and clinical relevance: Azathioprine appeared to be a safe and potentially effective adjunct to prednisone for treatment of dogs with MUE. Prospective, double-blinded, controlled studies with histologic confirmation are warranted to substantiate these findings.