Chronic progressive polyarthritis in a female cat.

Feline chronic progressive polyarthritis is a rare immune-mediated disease that has only previously been reported in male cats. A one-year-old female cat was presented with anorexia, lassitude and lameness. The tarsal, carpal and elbow joints revealed swelling, pain, stiffness, crepitus and regional lymphadenopathy, and fever was present. The cat was clinically diagnosed with chronic progressive polyarthritis based on the fever, swelling of joints, imaging of erosive proliferative periosteal polyarthritis, positivity for antinuclear antibody, synovial fluid analyses and urinalyses. Both feline leukemia virus antigen and feline immunodeficiency virus antibody were positive. Using hair root DNA, polymerase chain reaction amplification targeting the sex-determining region on the Y chromosome gene amplified the fragment of DNA from a normal male cat, but not amplified from a normal female cat or the present cat. Accordingly, the present cat was classified as genetically female. Cyclosporine treatment was started, and the general condition and movement quickly improved and continued for 8 months post-diagnosis. This is the first report of chronic progressive polyarthritis in a female cat.