Canine immune-mediated polyarthritis

Immune-mediated polyarthritides (PA) are defined by synovial inflammation, failure to identify a microbial aetiology and response to immunosuppressive therapy. These diseases have common immunopathogenic features and may be subdivided into erosive (e.g., rheumatoid arthritis [RA]) and non-erosive forms (e.g., “idiopathic“ polyarthritis (IPA) type I; type II associated with infectious disease; type III with gastrointestinal disease; type IV with neoplasia; vaccination reactions, systemic lupus erythematosus, and others). Typical clinical findings are a stiff gait, varying degrees of lameness, shifting leg lameness, fever, and bilaterally symmetrical swollen painful joints. Diagnosis is based on radiographs, arthrocentesis and synovial fluid analysis of several joints. Blood and urine analyses, and diagnostic imaging of thorax and abdomen are helpful in identification or exclusion of underlying diseases. Further diagnostic testing is recommended in certain cases such as serology / PCR testing for infectious diseases, CSF analysis, cytology of lymph nodes, etc.
In IPA II – IV treatment is primarily directed against the underlying disease. If RA, IPA I or a vaccination reaction is suspected analgesics and often doxycycline are given initially. In most cases of IPA I and RA immunosuppressive therapy with prednisolone (and sometimes other immunosuppressive agents) is necessary. IPA type I has a favourable prognosis and cure is possible, but the recurrence rate is high. Prognosis for vaccination reactions and IPA II – IV is good if the underlying disease can be treated.