Rheumatology
Core concepts
Rheumatoid arthritis: symmetrical small-joint synovitis, morning stiffness over an hour, anti-CCP (more specific than rheumatoid factor), erosions; treat early with methotrexate and escalate to biologics; know extra-articular disease (nodules, interstitial lung disease, vasculitis, Felty's syndrome, cervical subluxation). Spondyloarthritis: inflammatory back pain, sacroiliitis, HLA-B27, associated psoriasis, uveitis and inflammatory bowel disease, with asymmetric large-joint and entheseal involvement. Crystal arthritis: gout (negatively birefringent needle-shaped urate crystals, podagra; treat the flare with NSAID, colchicine or steroid, then lower urate to target) versus pseudogout (positively birefringent rhomboid calcium pyrophosphate crystals, chondrocalcinosis, knees and wrists, associated with haemochromatosis, hyperparathyroidism and hypothyroidism). SLE: malar rash, photosensitivity, serositis, cytopenias; ANA is sensitive, anti-dsDNA and anti-Sm specific, anti-Ro causes neonatal lupus; complement is consumed. Vasculitis: giant cell arteritis (over 50, headache, jaw claudication, visual loss - give steroids immediately, do not wait for biopsy), ANCA-associated vasculitides, polyarteritis nodosa. Myositis: proximal weakness, raised creatine kinase, anti-Jo1, malignancy screen.
Traps
Missing septic arthritis in a hot single joint - aspirate before giving steroids. Diagnosing gout without seeing crystals. Forgetting that rheumatoid factor is nonspecific and anti-CCP may precede symptoms by years.
Rule of thumb
A hot single joint in a febrile patient is septic until microscopy says otherwise: aspirate, send for Gram stain and crystals, and start empirical antibiotics.