Intra-articular organisms are not always cytologically detectable in dogs with blastomycosis-associated inflammatory arthritis.

Abstract

OBJECTIVE: To describe the clinical, cytologic, and radiographic features of inflammatory arthritis associated with blastomycosis in dogs. METHODS: This study included 12 dogs with blastomycosis and cytologic evidence of inflammation in at least 1 joint identified at a tertiary referral center over a 25-year period. Median age of presentation was 5.0 (1.1 to 9.0) years, and 4 of 12 cases were Labrador Retrievers. Musculoskeletal signs were the primary complaint for 10 dogs, while the other 2 presented for respiratory concerns. All dogs were lame upon evaluation, and 10 of 12 had palpable joint swelling. All dogs had evidence of blastomycosis in at least 1 other body system. RESULTS: Of 25 joint fluid cytologies, interpretations consisted of inflammatory arthritis in 21 joints (12 dogs), degenerative joint disease in 1 joint (1 dog), and unremarkable in 3 joints (2 dogs). The inflammation was categorized as suppurative (17 joints, 11 dogs) or pyogranulomatous (4 joints, 1 dog). Intra-articular Blastomyces organisms were observed in 10 joints (6 dogs). Eight of 9 joints (7 of 8 dogs) imaged had at least 1 radiographic abnormality, including 5 joints with osteolytic lesions. All bony lesions were periarticular. Ten dogs received oral antifungal drugs. Three dogs died within 1 month of evaluation; all 6 dogs with long-term follow-up achieved blastomycosis remission, but 2 required surgical arthrodesis of affected joints. CONCLUSIONS: Not all dogs with blastomycosis-associated arthritis have cytologically detectable organisms in their joint fluid. CLINICAL RELEVANCE: Unlike other sampling sites where pyogranulomatous inflammation predominates, suppurative inflammation is most common in the joints.