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Objectives To investigate whether there is a temporal relationship between vaccination and the onset of type 1 immune-mediated polyarthritis in dogs. Materials and Methods Retrospective case–control study: 39 dogs from a referral hospital with a diagnosis of type 1 immune-mediated polyarthritis were age-matched with 78 control dogs with other diagnoses. A temporal association between vaccination and polyarthritis was considered positive if recent vaccination had been performed within 28 days of the onset of clinical signs of immune-mediated polyarthritis. The odds ratio association of recent vaccination with immune-mediated polyarthritis was calculated using matched case–control methods. Results Of the 39 dogs in the type 1 immune-mediated polyarthritis group, four had been vaccinated within 28 days before onset of clinical signs compared to six dogs in the control group. The odds ratio for a dog developing type 1 immune-mediated polyarthritis if vaccinated within the last 28 days was estimated to be 1·44 (95% confidence interval 0·25 to 8·24, P = 0·88). Clinical Significance There was no evidence of a temporal relationship between vaccination and type 1 immune-mediated polyarthritis, although the large confidence interval on the odds ratio suggests a need for larger studies to confirm this finding.

Case summary A 7-year-old neutered male Norwegian Forest Cat was presented with decreased appetite and activity, weight loss, fever, neutrophilia and hyperglobulinaemia. A physical examination showed painful stifle joints and enlarged popliteal lymph nodes. Blood examination showed neutrophilia, hyperglobulinaemia and increased serum amyloid A. Urinalysis, thoracic and abdominal radiographs, and abdominal ultrasonography were unremarkable. Synovial fluid from the knee joints had diminished viscosity and revealed neutrophilic inflammation on the smear. There was no evidence of infection in a microbiological culture of the synovial fluid. A diagnosis of idiopathic immune-mediated polyarthritis (IMPA) was made. Prednisolone was initiated at 2 mg/kg q24h PO and tapered with additional immunosuppressants (leflunomide, ciclosporin A and methotrexate); however, prednisolone could not be discontinued. Informed consent was obtained from the owner and mycophenolate mofetil (MMF) at a dosage of 10 mg/kg q12h PO was initiated on day 798. There were no adverse effects of MMF and prednisolone was discontinued on day 1183. Clinical signs resolved and the cat’s general condition remained stable with MMF alone at a dosage of 10 mg/kg q48h PO on day 1600. Relevance and novel information There is limited information describing feline IMPA and its treatment options other than the use of prednisolone. This is the first report of the successful treatment and long-term follow-up of feline IMPA with MMF. MMF may be a safe and effective option as an additional immunosuppressant in feline IMPA.

Inflammatory arthritis occurs much less frequently than degenerative joint disease in cats. Synoviocentesis is essential in confirming a diagnosis but extensive testing may be required in order to determine the underlying cause. Inflammatory arthritis is classified into infectious and non-infectious and erosive or non-erosive forms, and differentiating between these is important when deciding on appropriate therapeutics and in giving owners an accurate prognosis. Idiopathic immune-mediated polyarthritis is relatively rare in cats in comparison to dogs, with infectious causes of inflammatory arthritis being far more common. It is critical therefore that both infectious and neoplastic causes of polyarthritis are definitively ruled out before considering treatment with immunosuppressive drugs.

Canine immune-mediated polyarthritis (IMPA) is a diagnosis of exclusion based predominantly on clinical signs, characteristic joint fluid analysis, and elimination of potential joint infection. Ultimately, an appropriate and sustained response to immunosuppressive therapy may become the final diagnostic criterion used. Identifying associated disease processes, including breed-specific syndromes, remote infection, inflammation, drug exposure, vaccine exposure, or neoplasia, as well as initial response to therapy, is often an important contributor to prognosis. This review article is the second of a two part series and focuses on the diagnosis and treatment of immune-mediated polyarthritis. The first article in this series, published in the January/February 2012 issue, concentrated on the pathophysiology of IMPA.

Objective—To evaluate efficacy and adverse effects of leflunomide for the treatment of naturally occurring immune-mediated polyarthritis (IMPA) in dogs. Design—Retrospective case series. Animals—14 dogs with cytologically confirmed IMPA. Procedures—Medical records were used to identify dogs with a diagnosis of IMPA that were treated with leflunomide. Signalment, radiographic findings, laboratory data, dosage of leflunomide, treatment duration, treatment response, and occurrence of adverse effects were determined from medical records. Results—Mean ± SD initial dosage of leflunomide was 3.0 ± 0.5 mg/kg (1.4 ± 0.2 mg/lb) PO once daily. Treatment duration for the initial starting dosage ranged from 1 to 6 weeks. Of the 14 dogs treated with leflunomide, 8 had complete resolution of clinical signs of IMPA initially, 5 had partial response to treatment, and 1 had minimal response to treatment. Adverse effects from treatment with leflunomide were not observed during the treatment period. Conclusions and Clinical Relevance—Oral administration of leflunomide was a safe and effective alternative to oral administration of corticosteroids for treatment of IMPA in dogs. On the basis of findings in this study, a starting dosage for leflunomide of 3 to 4 mg/kg (1.4 to 1.8 mg/lb) PO once daily for at least 6 weeks before making dose adjustments is recommended. Dose adjustments should be based on cytologic evaluation of synovial fluid and clinical signs of IMPA. Hematologic variables, serum biochemical analysis results, and clinical signs of IMPA should be monitored for evidence of adverse effects to treatment with leflunomide.

Objective—To determine clinical signs, laboratory findings, relationship to vaccination, and response to treatment for type I immune-mediated polyarthritis (IMPA) in dogs. Design—Retrospective study. Animals—39 dogs. Procedure—Clinical records and radiographic reports from 3 university referral hospitals were reviewed. Clinical signs, laboratory and investigative findings, relationship to vaccination, and response to treatment were evaluated. Results—Clinical signs and initial laboratory and clinical investigative findings were frequently abnormal but were nonspecific and not associated with likelihood of recovery. Time of vaccination was not associated with onset of disease. Chemotherapeutic immunosuppression resulted in complete cure in 56% of dogs. Continuous medication was required in 18% (7/39) of dogs, relapses were treated successfully in 13% (5/39) of dogs, and 15% (6/39) of dogs died or were euthanatized as a result of disease. Conclusions and Clinical Relevance—The possible involvement of vaccination in type I IMPA was not made clear from this study because of the small population size. Signalment, clinical signs, and results of diagnostic tests other than multiple synovial fluid analyses were generally nonspecific. Most dogs with type I IMPA responded to initial immunosuppressive treatment, but 31% (12/39) of dogs relapsed, required further treatment, or both. (J Am Vet Med Assoc 2004;224:1323–1327)

Background Monitoring systemic inflammatory activity during steroid therapy of canine immune-mediated polyarthritis (IMPA) is difficult and mainly relies on clinical signs. Case presentation Canine serum C-reactive protein (CRP) was measured serially and blinded during a 27-week follow-up period of a case of Anaplasma phagocytophilia induced type II immune-mediated polyarthritis. Conclusion WBC was, as expected, observed not to reflect the inflammatory activity during steroid treatment in a clinical useful manner, whereas, CRP is suggested a valuable unbiased marker of inflammatory activity during steroid treatment in this case.