Clinical meaning
SLE features loss of tolerance to nuclear antigens with anti-dsDNA and anti-Smith antibodies. Immune complex deposition activates complement (C3, C4 consumption). ACR/EULAR 2019 criteria use ANA as entry criterion. Hydroxychloroquine is cornerstone therapy reducing flares and thrombotic risk.
Diagnosis & workup
Diagnostics & workup: - ANA with reflex to specific antibodies (anti-dsDNA, anti-Smith, anti-SSA/SSB) - ANCA panel (c-ANCA/PR3, p-ANCA/MPO) for vasculitis evaluation - Rheumatoid factor and anti-CCP antibodies for RA - Synovial fluid analysis: WBC count, culture, crystal examination - Uric acid level (not diagnostic during acute gout flare) - Joint aspiration with crystal analysis (MSU for gout, CPPD for pseudogout) - X-ray of affected joints (erosions, joint space narrowing, calcifications)
Risk factors: - Medication-induced lupus (hydralazine, procainamide, isoniazid) - Prior joint trauma or overuse - Female sex (SLE, RA, Sjogren: 9:1 female predominance) - Vitamin D deficiency associated with autoimmune disease risk - Autoimmune disease clustering (thyroid + RA + Sjogren) - Genetic predisposition (HLA-B27 for AS, HLA-DR4 for RA) - Smoking (strongest environmental risk for RA, dose-dependent)