Clinical meaning
ANCA-associated vasculitis includes GPA (c-ANCA/PR3), MPA (p-ANCA/MPO), and EGPA (eosinophilia + p-ANCA). These small-vessel vasculitides cause necrotizing inflammation with pauci-immune glomerulonephritis. GPA: upper/lower respiratory tract granulomas with renal involvement. MPA: rapidly progressive GN without granulomas. Treatment: induction with cyclophosphamide or rituximab + glucocorticoids, then maintenance with rituximab or azathioprine.
Diagnosis & workup
Diagnostics & workup: - X-ray of affected joints (erosions, joint space narrowing, calcifications) - Complement levels (C3, C4: decreased in active SLE) - MRI for early erosive disease detection before X-ray changes - CBC (cytopenias in SLE), CMP, urinalysis (lupus nephritis) - HLA-B27 testing for seronegative spondyloarthropathy - ANA with reflex to specific antibodies (anti-dsDNA, anti-Smith, anti-SSA/SSB) - Rheumatoid factor and anti-CCP antibodies for RA
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)