SLE
Summary
Systemic Lupus Erythematosus (SLE) is a chronic autoimmune disease characterized by production of autoantibodies (notably ANA and anti-dsDNA) that cause multisystem inflammation and tissue damage. It predominantly affects women of childbearing age, especially African American, Hispanic, and Asian populations. Classic features include malar rash, arthritis, serositis, nephritis, and hematologic/neurologic abnormalities.
Detail
SLE is a type III (immune complex-mediated) hypersensitivity disease driven by loss of self-tolerance, leading to production of autoantibodies against nuclear antigens (ANA, anti-dsDNA, anti-Smith). Immune complexes deposit in tissues (skin, joints, kidneys, serosa, CNS, blood vessels), activating complement and causing inflammation. Diagnosis uses the SLICC/ACR criteria, requiring a combination of clinical and immunologic criteria (e.g., malar 'butterfly' rash, discoid rash, photosensitivity, oral ulcers, nonerosive arthritis, serositis (pleuritis/pericarditis), renal disorder (proteinuria/casts), neurologic disorder (seizures/psychosis), hematologic abnormalities (hemolytic anemia, leukopenia, thrombocytopenia), and positive ANA/anti-dsDNA/anti-Sm). Anti-dsDNA correlates with disease activity and lupus nephritis; anti-Smith is highly specific but not sensitive. Drug-induced lupus (procainamide, hydralazine, isoniazid, quinidine) is associated with anti-histone antibodies and typically spares the kidneys/CNS, resolving after drug discontinuation. Lupus nephritis is classified by WHO/ISN classes (I–VI), with class IV (diffuse proliferative) being most severe, showing 'wire-loop' capillaries and subendothelial immune complex deposits on EM; 'full house' immunofluorescence (IgG, IgA, IgM, C3, C1q) is classic. Antiphospholipid antibody syndrome (lupus anticoagulant, anticardiolipin, anti-β2-glycoprotein I) often coexists, causing hypercoagulability, recurrent miscarriages, and false-positive VDRL/RPR. Libman-Sacks endocarditis (verrucous, nonbacterial vegetations on mitral valve, often undersurface) is a classic cardiac manifestation. Treatment includes NSAIDs and hydroxychloroquine for mild disease, corticosteroids and immunosuppressants (mycophenolate, cyclophosphamide, azathioprine) for severe/organ-threatening disease, and belimumab or rituximab for refractory cases. Complications include increased infection risk (from immunosuppression), accelerated atherosclerosis, and renal failure. Drug-induced lupus and neonatal lupus (from anti-Ro/SSA crossing placenta, causing congenital heart block) are important boards associations.
Sources
- First Aid for the USMLE Step 1
- Robbins and Cotran Pathologic Basis of Disease
- UpToDate: Systemic Lupus Erythematosus
- Kaplan USMLE Step 1 Lecture Notes - Immunology
Reviewed by Medusa editorial — medical student review. Information here is for study reference only and is not medical advice. Spotted an error? Let us know.