Recognizing and treating immune-mediated polyarthritis in dogs - Veterinary Medicine
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Recognizing and treating immune-mediated polyarthritis in dogs
This inflammatory joint condition presents in many forms, often causing systemic illness and sometimes causing cartilage and bone destruction. Learn to distinguish these forms and what treatments induce remission and alleviate pain.


VETERINARY MEDICINE


Idiopathic

Idiopathic nonerosive polyarthritis is the most common form of IMPA and represents 58% to 83% of all reported cases of IMPA.1,5,8,9 Idiopathic nonerosive polyarthritis has been classified into four subtypes depending on the presence of distant infection, gastrointestinal disease, or neoplasia (Table 1). The relevance of associated disease in canine IMPA is unknown, but similar associations are recognized in people and are thought to have pathogenic significance by acting as a trigger for IMPA.15 Idiopathic types II, III, and IV are also referred to as reactive IMPA by some authors.2,8

Idiopathic type I IMPA is not associated with distant disease and accounts for most idiopathic nonerosive IMPA cases reported in dogs.5,7,8,15 Idiopathic type II IMPA is associated with infectious or chronic inflammatory disease and has been reported with pyoderma, urinary tract infection, pneumonia, endocarditis, mastitis, dirofilariasis, fungal infection, pleuritis, and severe periodontal disease.1,5,8,15 Idiopathic type III IMPA is associated with chronic gastrointestinal disease and has been reported with inflammatory bowel disease, intestinal malabsorption, bacterial overgrowth, and ulcerative colitis.1,5,8,15 Idiopathic type IV IMPA is associated with distant neoplasia and has been reported with squamous cell carcinoma, mammary adenocarcinoma, leiomyoma, heart base tumor, and seminoma.1,5,8,15

Treating idiopathic type I IMPA involves administering immunosuppressive, immunomodulating, and disease-modifying agents, while treating idiopathic types II, III, and IV focuses on resolving the underlying disease process. The prognosis of idiopathic type I IMPA is good to guarded, while idiopathic types II through IV have a variable prognosis depending on the treatability of concurrent disease.1,5,7,8,15

SLE polyarthritis

Systemic lupus erythematosus (SLE) is a progressive multiorgan autoimmune disease in which polyarthritis is one of the most frequently observed clinical findings. SLE preferentially afflicts male German shepherds and other medium- and large-breed dogs; it is diagnosed at a mean age of 5 years.1,6,11-13,16,17 Clinical signs of SLE can be intermittent and include polyarthritis, hemolytic anemia, thrombocytopenia, glomerulonephritis, polymyositis, skin lesions, fever of unknown origin, oral ulceration, and lymphadenopathy (Table 2).


Table 2
Because of its variable presentation and progressive nature, SLE is often difficult to diagnose early in its course. Later in the disease process when other clinical manifestations appear, SLE may be more readily diagnosed. SLE is definitively diagnosed when two major signs and positive serologic test results are present or one major and two minor signs and positive serologic test results are present (Table 2).13 A probable diagnosis is made with one major sign and positive serologic test results or two major signs and negative serologic test results (Table 2).13 SLE polyarthritis has a similar presentation to other nonerosive forms of IMPA and reportedly accounts for 8% to 20% of canine IMPA cases.2,5,8,17,18

The treatment of SLE polyarthritis is similar to the treatment of idiopathic forms and requires administering immunosuppressive and immunomodulating medications. If other organ systems are involved, treatment must also address other clinical signs. Remission is attainable with treatment and may also occur spontaneously.6,13 The prognosis of SLE is variable, and concurrent organ dysfunction is often responsible for death or euthanasia.

Polyarthritis-meningitis syndrome

A syndrome in which steroid-responsive meningitis arteritis (SRMA) occurs with polyarthritis has been described.1,6,10,16 It was first seen in Bernese Mountain dogs, Weimaraners, and German shorthaired pointers but has since been documented in many breeds.10 In one study, 29% of dogs with IMPA had associated spinal pain, and, of those, nearly 50% were confirmed to have concurrent SRMA by cerebrospinal fluid (CSF) analysis.10

Dogs with polyarthritis-meningitis syndrome are suspected to have spinal pain due to a combination of meningeal and intervertebral joint inflammation.10 Polyarthritis-meningitis syndrome occurs in young, male, medium- to large-breed dogs, and clinical signs include lethargy, reluctance to walk, and cervical pain, particularly on flexion and extension of the neck.1,6,10 Effusion involving appendicular joints may not be obvious.6

The treatment of SRMA and IMPA is similar, but the syndrome is important to recognize since recurrence or neurologic damage may occur if it is treated inappropriately.10,19 Most dogs with SRMA respond to immunosuppressive therapy with a good to guarded prognosis. It is not known whether dogs with both IMPA and SRMA have a different prognosis than dogs with SRMA alone.10


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Source: VETERINARY MEDICINE,
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