Auricular Chondritis Associated with Systemic Joint and Cartilage Inflammation in a Cat

An adult, Japanese domestic cat presented with bilateral swelling, distortion, and erythema of ears and deformation of the limbs. Biopsy of the pinnae confirmed auricular chondritis. These lesions and the cat's general condition subsequently deteriorated, and the cat died. At necropsy, chondral changes were present in the pinnae, costae, larynx, trachea, and limbs. Histopathologically, these chondral tissues showed marked deformation with lymphocytic inflammation. The limb joint inflammation was associated with chondral erosion, deformation of subchondral bones with pannus, and thinning of cancellous bones. These lesions were consistent with the diagnostic criteria for human relapsing polychondritis. However, the cat had erosive arthritis, which appeared to be different from human relapsing polychondritis.