A female Beauceron was presented for lethargy, fever, and ulcerated skin lesions along the dorsal trunk. The signs progressed despite antibiotic therapy and in a few days the dog was suffering from tri-cavitary effusion as well as a polyarthropathy. Histopathology results from skin biopsy specimens revealed chronic pyogranulomatous septal panniculitis with no bacterial growth and no fungal organisms noted with special stains. These results were suggestive of an immune-mediated etiology. Immunomodulatory therapy was begun and signs quickly resolved. This paper will discuss the differential diagnoses for tri-cavitary effusion, pyogranuomatous septal panniculitis, and polyarthropathy.