Systemic Lupus Erythematosus
Rheumatology
Illness script · Rheumatology
Systemic Lupus Erythematosus
Systemic autoimmune disease causing multi-organ inflammation via autoantibodies and immune complex deposition, with relapsing-remitting course.
This illness script for Systemic Lupus Erythematosus 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 (9:1 female-to-male ratio)
- African American, Hispanic, Asian women disproportionately affected
- Peak onset ages 15–45
- Drug-induced SLE: hydralazine, procainamide, isoniazid (anti-histone Ab)
- UV light exposure triggers flares
- Genetic: HLA-DR2, HLA-DR3, C1q/C4 complement deficiencies
02
Presentation
- Malar (butterfly) rash: fixed erythema over cheeks sparing nasolabial folds
- Photosensitivity, discoid rash, painless oral ulcers
- Arthritis: non-erosive, symmetric, small joints (Jaccoud arthropathy)
- Serositis: pleuritis or pericarditis (sharp chest pain, positional)
- Nephritis: hematuria, proteinuria, hypertension — major mortality driver
- Neuropsychiatric SLE: psychosis, seizures; cytopenias (hemolytic anemia, thrombocytopenia, lymphopenia)
03
Pathophysiology
- Defective clearance of apoptotic cells → nuclear antigen exposure
- Autoreactive B and T cells generate pathogenic autoantibodies (anti-dsDNA, anti-Sm)
- Immune complex deposition (type III hypersensitivity) → complement activation → tissue inflammation
- Anti-dsDNA titers correlate with disease activity; low complement (C3/C4) during flares
04
Diagnostics
- ANA: highly sensitive (~99%) but not specific — best screening test
- Anti-dsDNA: highly specific (~70%), tracks disease activity, correlates with nephritis
- Anti-Smith (anti-Sm): most specific (~99%) but low sensitivity (~30%)
- Anti-Ro/SSA, anti-La/SSB: associated with neonatal lupus and congenital heart block
- Urinalysis + urine protein:creatinine ratio to screen for nephritis; renal biopsy for class staging
- Complement levels (C3, C4) drop during active disease — useful to monitor flares
05
Management
- Hydroxychloroquine (HCQ): first-line for all SLE patients; reduces flares and mortality
- NSAIDs and low-dose corticosteroids for mild-to-moderate disease (arthritis, serositis)
- Moderate-to-severe disease (nephritis, CNS): high-dose corticosteroids + mycophenolate or cyclophosphamide
- Belimumab (anti-BLYS): approved add-on for active serologic disease
- Strict sun protection; avoid estrogen-containing OCP in antiphospholipid antibody-positive patients
- Monitor for hydroxychloroquine retinal toxicity with annual ophthalmology exam
06
Clinical pivots
How to separate this script from the look-alikes that show up on exams and on the wards.
Rheumatoid Arthritis
RA causes erosive joint disease with positive RF/anti-CCP; SLE arthritis is non-erosive with positive ANA/anti-dsDNA
Drug-Induced Lupus
Drug-induced SLE spares kidneys/CNS, is anti-histone Ab positive (not anti-dsDNA), and resolves with drug discontinuation
Dermatomyositis
Dermatomyositis features proximal muscle weakness, elevated CK, heliotrope rash, and Gottron's papules — not malar rash
Antiphospholipid Antibody Syndrome
APS causes thrombosis and recurrent pregnancy loss without the multi-system inflammation; can co-exist with SLE (secondary APS)
Keep reading
Full library- Subarachnoid HemorrhageBleeding into the subarachnoid space, most often from a ruptured intracranial aneurysm, causing sudden severe headache.
- Systemic Lupus Erythematosus (SLE)Chronic autoimmune disease with multi-organ involvement driven by loss of tolerance to nuclear antigens and immune complex deposition.
Educational use only. This illness script is a study framework, not medical advice. Confirm decisions with current guidelines and your clinical supervisors.