Chronic multi-organ autoimmune disease where nuclear autoantibodies form immune complexes that damage multiple organs; classically presents with a 'butterfly' malar rash.
Relatively common and prototypical connective tissue disease. Primarily affects young women (~90% of cases) and can range from mild to life-threatening. Early recognition is crucial to prevent organ damage (e.g., renal failure from lupus nephritis) and improve survival.
Typically a woman of childbearing age with fatigue, fever, and migratory joint pains, plus skin findings like a photosensitive malar rash (spares nasolabial folds) or oral ulcers. May have alopecia and Raynaud phenomenon.
Polyarthritis (nonerosive) is very common (often in hands, wrists, knees) and can flare and remit. Any organ system can be involved: serositis (pleuritic chest pain, pericarditis), renal issues (hematuria or proteinuria from lupus nephritis), neurologic symptoms (seizures, psychosis), and hematologic abnormalities (hemolytic anemia, leukopenia, thrombocytopenia).
Lab clues: almost all SLE patients have a positive ANA (highly sensitive). More specific antibodies include anti-dsDNA (seen in ~60%, often indicates renal involvement) and anti-Sm. Often there are low complement levels (C3, C4) during active disease flares.
Suspect SLE when a patient has multisystem symptoms (especially a combination of skin + joint + internal organ findings). Rule out infections that can mimic SLE flares (e.g., fever in SLE can also indicate infection due to immunosuppression).
Initial test: ANA (highly sensitive but not specific); if positive, follow up with specific antibodies (like anti-dsDNA, anti-Sm, antiphospholipid panel) to confirm and assess disease. Also get baseline studies: urinalysis (for proteinuria/hematuria), kidney function, CBC, and inflammatory markers.
Use classification criteria (e.g., ACR or EULAR/ACR 2019) as a guide — ≥4 of the 11 classic criteria ("MD SOAP BRAIN") or sufficient weighted criteria points support the diagnosis.
If lupus nephritis is suspected (proteinuria, active urinary sediment), consider a renal biopsy to determine the class of nephritis (I–VI). This guides therapy (e.g., Class III/IV require aggressive immunosuppression).
overlap of SLE, scleroderma, polymyositis features; high anti-RNP antibody
Hydroxychloroquine for nearly all patients (reduces flares and improves long-term survival); plus general measures (sun avoidance, cardiovascular risk management).
For acute flares or serious organ involvement, use corticosteroids (e.g., high-dose prednisone); if life-threatening (e.g., severe nephritis, CNS lupus), treat with IV methylprednisolone and add a cytotoxic agent like cyclophosphamide or high-dose mycophenolate mofetil to induce remission.
Maintenance and steroid-sparing meds: azathioprine or mycophenolate (often after cyclophosphamide for lupus nephritis), or methotrexate for chronic arthritis/serositis. Biologic therapies like belimumab (anti-BLyS) can reduce flares in refractory SLE; newer drugs (voclosporin for nephritis, anifrolumab) are available for severe cases.
If antiphospholipid syndrome is present (clotting or pregnancy losses), patients require long-term anticoagulation (warfarin, or heparin + aspirin in pregnancy) to prevent thromboses.
Mnemonic: MD SOAP BRAIN to recall the 11 classic criteria (Malar rash, Discoid rash, Serositis, Oral ulcers, Arthritis, Photosensitivity, Blood cytopenias, Renal disorder, ANA positivity, Immunologic markers, Neurologic symptoms).
Anti-dsDNA titers often correlate with disease activity, especially for lupus nephritis; rising anti-dsDNA and dropping complement levels can foreshadow a flare.
Libman-Sacks endocarditis is a non-infectious endocarditis due to SLE (sterile vegetations on both sides of valves) – rare but classic for boards.
Lupus nephritis: new proteinuria, RBC casts, or rising creatinine → needs prompt evaluation (often biopsy) and aggressive therapy to prevent permanent kidney damage.
Neuropsychiatric lupus: seizures, psychosis, or severe headaches → indicates CNS involvement; hospitalize and treat aggressively (high-dose steroids, immunosuppressants) after ruling out infection.
Antiphospholipid syndrome: any SLE patient with unexplained clot (DVT, stroke) or recurrent miscarriage → suspect APS (hypercoagulability) and initiate anticoagulation promptly.
Compatible signs (photosensitive rash, arthritis, etc.) → test ANA.
If ANA positive → further tests: anti-dsDNA, anti-Sm, antiphospholipid antibodies; plus labs (CBC, metabolic panel, UA, complement levels).
If criteria are sufficient and other causes excluded → confirm SLE diagnosis (2019 EULAR/ACR criteria: ANA ≥1:80 required, then weighted clinical/immunologic criteria ≥10 points).
Assess organ involvement: e.g., kidney (if proteinuria → biopsy), CNS (imaging, LP if indicated), etc., to guide therapy intensity.
Treat accordingly: hydroxychloroquine for all; steroids ± immunosuppressants for flares as needed. Coordinate care with specialists (rheumatology, nephrology) and monitor for flares or complications at follow-up.
Young African-American woman with a facial rash, joint pain, and proteinuria (RBC casts) → SLE (lupus nephritis).
Female patient with SLE having recurrent pregnancy losses and arterial/venous thromboses → think antiphospholipid syndrome (hypercoagulability with lupus anticoagulant, anticardiolipin antibodies).
SLE patient with chest pain and pericardial friction rub → pericarditis from lupus (serositis).
Case 1
A 24‑year‑old woman reports fatigue, joint pains, and a facial rash that worsens with sun. Exam shows an erythematous malar rash sparing the nasolabial folds and tenderness in the small joints of her hands. Labs: ANA titer 1:640, anti-dsDNA positive, hemoglobin 10 (low), platelets 110k (low), creatinine 1.8 mg/dL, urinalysis with proteinuria and RBC casts.
Case 2
A 30‑year‑old woman with SLE has had two miscarriages and now presents with acute left leg swelling. Doppler ultrasound confirms a DVT. Her lab tests show a positive lupus anticoagulant and anti-cardiolipin antibodies.
Illustration of systemic lupus erythematosus with a butterfly rash on the face and multiple organs involved, plus an inset photo of the classic malar rash.
