Feline immune‐based polyarthritis: a study of thirty‐one cases

Non‐infective polyarthritis in the cat is classified into erosive (feline rheumatoid arthritis and feline periosteal proliferative polyarthritis) and non‐erosive (feline systemic lupus erythematosus, feline idiopathic polyarthritis) forms. Criteria are used to identify each group. Clinically, all forms are similar. Affected cats are stiff, unwilling to move and may resent any form of handling. Joints are usually swollen and painful on manipulation. Some cases are pyrexic and inappetent. Radiography demonstrates destructive changes within joints in the erosive forms and also the periosteal new bone, characteristic of the periosteal proliferative form. Soft tissue thickening is also demonstrated. Tests for the autoantibodies rheumatoid factor and antinuclear antibody are important in the diagnosis of rheumatoid arthritis and systemic lupus erythematosus. Treatment is with anti‐inflammatory and immunosuppressive agents (prednisolone, cytotoxic drugs). Cats with the rheumatoid and periosteal proliferative types do not recover but some manage to cope with the lameness. Cats with idiopathic polyarthritis can make a complete recovery although cases associated with myeloproliferative disease have a hopeless prognosis.