Polyarthritis: Clinical approach to medical joint disease (Proceedings)

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Polyarthritis: Clinical approach to medical joint disease (Proceedings)

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Apr 01, 2010

Nontraumatic inflammatory joint disease is a relatively common, but under-recognized, cause of fever and morbidity in dogs. In one review of 66 dogs referred for fever of unknown origin to a veterinary teaching hospital, approximately 8% were diagnosed with immune-mediated polyarthritis. In addition to immune-mediated polyarthritis (i.e. inflammatory joint disease in the absence of an underlying genetic, infectious, or other secondary cause) there are a number of additional syndromes that have been recognized in dogs and cats. This lecture will review the general approach to non-traumatic joint disease in small animal patients, the differential diagnoses encountered in dogs and cats, and then review the clinical features and treatment of immune-mediated polyarthritis in detail.

Definition and Differential Diagnosis

Polyarthritis is defined as inflammation in two or more joints. Although any joint may be affected, including the inter-vertebral joints, large proximal limb joints and small distal limb joints, it is the stifle, carpal, and tarsal joints which are usually most severely affected. In addition, swelling due to effusion is easiest to appreciate in these three sets of joints. Primary immune mediated polyarthritis is a type III hypersensitivity disorder—circulating immune complexes are deposited in the synovial membrane and initiate inflammation, recruitment of inflammatory cells, release of cytokines and proteolytic enzymes including metalloproteinases, with resultant pain, excess joint fluid production, and eventual cartilage degeneration. In secondary polyarthritis, immune complex deposition in the joints may occur secondary to any concurrent inflammatory/infectious or neoplastic disease. Some of the best recognized causes of secondary immune-mediated polyarthritis are the chronic tick-borne infectious agents, including Anaplasma spp, Ehrlichia spp, and Borrelia burgdorferi, in dogs, and a post-calicivirus vaccine transient polyarthritis that may occasionally be seen in cats.

The forms of immune-mediated polyarthritis described in dogs and cats include:

Non-erosive polyarthritides
• Idiopathic, immune-mediated polyarthritis (large breed dogs)
• Secondary immune-mediated polyarthritis (no breed predisposition)
• Breed-specific idiopathic non-erosive polyarthritis (described in young Akitas, Weimeraners, Newfoundlands)
• Shar-Pei polyarthritis (oftentimes associated with renal/systemic amyloidosis, also known as 'Shar-Pei fever')
• Lymphoplasmacytic synovitis (Rottweilers, Labrador Retreivers, Newfoundlands, Staffordshire Terriers)
• Systemic lupus erythematosus

Erosive polyarthritides
• Rheumatoid arthritis (small/toy breeds)
• Erosive polyarthritis of greyhounds (Greyhounds, usually young at onset of clinical signs)
• Feline chronic, progressive polyarthritis (high association with FeLV, young male cats)

Immune-Mediated Polyarthritis

      Epidemiology and Clinical Signs
Idiopathic, immune-mediated polyarthritis is most commonly diagnosed in young-to-middle aged large breed dogs. The median age of onset is approximately 5 years, but has been reported in dogs from 6 months to 12 years. The most common clinical signs reported by owners include unwillingness to rise, cervical pain, a 'saw horse,' or 'walking on eggshells' gait, and anorexia and lethargy. Abnormal physical examination findings oftentimes include shifting-leg lameness, joint swelling and pain, and fever. In one retrospective review of dogs with primary immune-mediated polyarthritis, approximately 55% of affected dogs had body temperatures greater than 103 F at the time of diagnosis. Cervical pain may be due to involvement of the intra-vertebral joints in the disease process, or because sterile meningitis-arteritis may occur concurrently in up to 50% of dogs with immune-mediated polyarthritis and neck pain. It is important to remember this association because dogs with polyarthritis are oftentimes misdiagnosed as having probably neurologic disease due to the obvious neck involvement; however, dogs with polyarthritis, even with concurrent meningitis-arteritis, have normal neurologic examinations. Patients with chronic untreated disease or with the less common but more rapidly progressive erosive forms of disease may have distorted or collapsed joints and resultant severe gait abnormalities that are unfortunately irreversible.