The differential Dx is extensive
The differential includes polyarthralgias such as viral polyarthritis, systemic rheumatic diseases, and osteoarthritis.
Viral polyarthritis is caused by rubella, parvovirus B194, alphaviruses, and hepatitis B. Symptoms can last from 3 days to several weeks, but rarely persist beyond 6 weeks; alphaviruses, however, can last 3 to 6 months.5 The common symptom triad includes fever, arthritis, and rash. Chikungunya is an example of an alphavirus that has become a global disease. Alphavirus arthritis can mimic seronegative RA and even satisfy the classification criteria for RA if the initial symptoms of fever and rash and history of travel to endemic regions are not appreciated.5
Systemic rheumatic diseases. Early RA may mimic the arthritis of systemic lupus erythematosus (SLE), Sjögren’s syndrome, dermatomyositis, or mixed connective tissue disease.6 In contrast to RA, these disorders generally have systemic features, such as rashes, dry mouth and eyes, myositis, or nephritis, and generate autobodies, which are not seen with RA. The CRP is often normal in patients with active SLE, even when the ESR is elevated.
Osteoarthritis (OA) can be confused with RA, particularly when small joints are involved. A thorough history helps elucidate the diagnosis. For example, OA of the fingers affects distal interphalangeal joints and is associated with Heberden’s nodes, while RA more commonly affects MCP and PIP joints. Swelling from OA is typically firm, while swelling due to RA is warm, boggy, and tender. Joint stiffness due to OA is worse with activity and generally lasts only a few minutes, while joint stiffness due to RA is worse at rest and lasts 30 minutes or more. X-rays show joint-space narrowing with OA, but no erosions or cysts. RF may be present at low levels in older patients with OA, while it is usually associated with high levels in patients with seropositive RA.
Continue to: Treat with disease-modifying antirheumatic drugs