Canine immune-mediated polyarthritis: A review of 84 cases in the UK between 2011 and 2021

Background: Immune -mediated polyarthritis (IMPA) is a well -recognised disease in dogs, but studies evaluating the response rates, relapse rates and long-term outcomes are scarce. Objectives: To provide an updated description of the signalment, clinical signs, clinicopathological findings, distribution between subgroups, rates of response and relapse and long-term outcome of 84 dogs diagnosed with IMPA at a single referral hospital. Methods: Dogs diagnosed with IMPA between January 2011 and December 2021 were identified. Dogs with neutrophilic inflammation in >= 2 joints were included. Cases with <1 month of follow-up, or those missing pertinent data, were excluded. Results: A total of 84 cases were included. An initial response was achieved in 77/84 (92%) cases. Of the cases that initially responded, 37/77 (48%) suffered at least one relapse and 18/77 (23%) suffered multiple relapses. Indefinite treatment was recommended in 17/84 (20%) cases. Of the 70 dogs for which at least 12 months of follow-up data were available, 12/70 (17%) were euthanised due to IMPA or for unknown reasons. Conclusion: IMPA carries a fair prognosis, but relapses occur in many cases and euthanasia due to relapsing or refractory disease is not uncommon.