Rheumatology and Immunology: Arthritis, Autoantibodies and Vasculitis
Core concepts
Rheumatology questions test the approach to monoarthritis, oligoarthritis and polyarthritis; septic arthritis; crystal arthritis; rheumatoid arthritis (RA); systemic lupus erythematosus (SLE); vasculitis; polymyalgia rheumatica and giant cell arteritis; myositis; and osteoporosis. Understand autoantibody utility: ANA is sensitive but not specific; anti-CCP and rheumatoid factor support RA; anti-dsDNA and anti-Smith are specific for SLE; ANCA patterns help classify vasculitis. Septic arthritis is a medical emergency requiring joint aspiration and prompt antibiotics.
Traps
A normal uric acid during acute gout does not exclude gout. Do not wait for joint aspiration if septic arthritis is likely; aspirate before antibiotics when feasible but do not delay treatment. ANA positivity is common in healthy people. Giant cell arteritis needs immediate high-dose corticosteroids; biopsy can be done within about two weeks without changing management. Avoid attributing all joint pain in older adults to osteoarthritis.
Worked example / rule of thumb
A 72-year-old has new temporal headache, jaw claudication, ESR 90 mm/h and visual blurring. Start high-dose prednisolone immediately and arrange temporal artery biopsy. Rule: in suspected giant cell arteritis with visual symptoms, steroids come before biopsy, not after.