Systemic Lupus Erythematosus (SLE)
Rheumatology
Illness script · Rheumatology
Systemic Lupus Erythematosus (SLE)
Chronic autoimmune disease with multi-organ involvement driven by loss of tolerance to nuclear antigens and immune complex deposition.
This illness script for Systemic Lupus Erythematosus (SLE) covers predisposing factors, classic presentation, mechanism, workup, management, and the clinical pivots that separate it from look-alikes—written for USMLE Step 1 and clerkship reasoning.
01
Predisposing factors
- Women of childbearing age (15–45 yrs); F:M ratio ~9:1
- African American, Hispanic, Asian women disproportionately affected
- HLA-DR2, HLA-DR3 genetic associations
- C1q/C2/C4 complement deficiencies predispose
- Drugs (procainamide, hydralazine, isoniazid) → drug-induced lupus
- UV light and EBV exposure are environmental triggers
02
Presentation
- Malar (butterfly) rash: fixed erythema sparing nasolabial folds; worsens with sun
- Discoid rash, photosensitivity, painless oral ulcers
- Non-scarring alopecia; Raynaud's phenomenon
- Serositis: pleuritis or pericarditis (positional chest pain)
- Arthritis: symmetric, non-erosive, often migratory
- Renal: proteinuria >0.5 g/day or cellular casts (lupus nephritis)
- Neuropsychiatric: seizures, psychosis; hemolytic anemia, thrombocytopenia
03
Pathophysiology
- Defective clearance of apoptotic debris exposes nuclear antigens
- B-cell autoreactivity → anti-dsDNA and anti-Smith antibodies
- Immune complex deposition in kidneys, skin, joints, vessels
- Complement activation and neutrophil infiltration → end-organ inflammation
04
Diagnostics
- ANA: >95% sensitivity — best screening test (low specificity)
- Anti-dsDNA: high specificity (~97%), correlates with disease activity and nephritis
- Anti-Smith (anti-Sm): most specific (~99%) but low sensitivity
- Low complement (C3, C4) during flare; anti-dsDNA rises with flares
- SLICC criteria: ≥4 of 11 criteria OR biopsy-proven lupus nephritis + ANA/anti-dsDNA
- Urinalysis + spot urine protein:creatinine to screen for nephritis
05
Management
- Hydroxychloroquine: mainstay for all SLE patients (reduces flares, mortality, thrombosis)
- NSAIDs/low-dose steroids for arthritis and serositis
- Moderate–severe flares: high-dose prednisone ± mycophenolate or azathioprine
- Lupus nephritis class III/IV: mycophenolate mofetil (or cyclophosphamide) + steroids
- Belimumab (anti-BLYS) or voclosporin for refractory/nephritis cases
- Avoid sulfa drugs and sun exposure; aggressive BP and lipid control
- Antiphospholipid syndrome co-existing → anticoagulation (warfarin) if thrombosis
06
Clinical pivots
How to separate this script from the look-alikes that show up on exams and on the wards.
Drug-Induced Lupus
Anti-histone antibodies positive; anti-dsDNA negative; resolves after stopping offending drug
Rheumatoid Arthritis
RA has erosive, deforming joint disease and anti-CCP; SLE arthritis is non-erosive
Sjögren Syndrome
Sjögren features sicca (dry eyes/mouth) prominently; anti-Ro/La positive without multi-organ involvement typical of SLE
Mixed Connective Tissue Disease (MCTD)
MCTD defined by anti-U1 RNP antibody and overlap features; lacks anti-dsDNA and Smith antibodies
Keep reading
Full library- Systemic Lupus ErythematosusSystemic autoimmune disease causing multi-organ inflammation via autoantibodies and immune complex deposition, with relapsing-remitting course.
- Tension PneumothoraxAir trapped under pressure in the pleural space causing mediastinal shift, obstructive shock, and cardiorespiratory collapse.
Educational use only. This illness script is a study framework, not medical advice. Confirm decisions with current guidelines and your clinical supervisors.