Acute polyarthritis means pain and swelling in > 3 joints lasting < 6 weeks. Diagnostic possibilities are large. Infection is the leading concern. Examples include viral (parvo virus, hepatitis B or C), and bacterial (endocarditis) infections.
Lyme disease typically produces a more indolent mono or oligoarticular course.
Tumors (acute leukemia, carcinoma) vasculitis (Wegenerís, temporal arteritis) and drug-induced SLE (hydralazine, procainanide) are considerations. Of course chronic inflammatory diseases have to start somewhere. RA is most commonly more slowly progressive over months, but acute presentations are not rare. Any of the other collagen vascular diseases (SLE, poly/dermatomyositis, scleroderma, Sjogrens syndrome) can begin in this fashion.
Finally spondyloarthropathes particularly psoriatic arthritis and Reiterís can have an acute presentation.
The history is the most important part of this patients evaluation and should be directed at identifying any symptoms of infection, prodromal syndromes, or recent exposure. Complete review of systems is important to identify any other organs involved, thereby identifying a multi-system disorder rather than isolated joint disease. Additionally the recognition of Raynaudís phenomenon, Sjogrenís symptoms, photosensitive rash, would point you in the direction of a collagen vascular disease. Eye inflammation, history of psoriasis, urethritis would raise concerns for a spondyloarthropathy.
A viral arthropathy is a strong consideration given her exposure history and prodromal symptoms. Rheumatoid arthritis is also possible. Given her age and sex would keep SLE and other collagen vascular diseases in the back of my mind even though there are no other supporting features at this time.
CBC, UA, LFTís and renal function should be done. Abnormalities would trigger further evaluation targeted to the involved organ. ESR is often ordered, but has little specificity, except for proportionate escalation in your concern for serious disease. ANA, RF are problematic in this case. Although we canít yet exclude SLE, there is no support for that diagnosis except her joint disease. Viruses commonly induce auto antibodies transiently. A positive RF might lead you to diagnosis RA, when the patient doesnít have it. Treatment in the first few weeks is not altered. Consider ordering antibodies in those patients who donít improve after 6 weeks, or develop other signs of collagen-vascular disease. X-rays are not helpful. If this were an older patient, crystal disease would be a consideration and joint aspiration should be done. Extensive viral serologies can be ordered, but will not alter initial management. Acute and convalescent sera are often required and the clinical course often answers the question before the titers are back!
If the patient has not already begun would use NSAIDís at inflammatory dose. Ibuprofen 600 mg OID is a reasonable choice.
This was likely a viral arthropathy. Parvo virus would be a typical culprit.