Conditions · Systemic conditions
Systemic lupus erythematosus !
Lupus (systemic lupus erythematosus) is a chronic autoimmune disease that inflames many organs, such as skin, joints and kidneys, in flares and remissions.
Updated 2026-10-30
Structures involved
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In biochemistry
In immunology
- Hypersensitivity: the four types compared
- Type III hypersensitivity (immune complexes)
- Immune tolerance and how autoimmunity begins
- Autoantibodies: the table to know
- HLA associations with disease
- Molecular mimicry and post-infectious autoimmunity
- Complement deficiencies and hereditary angioedema
- Complement: three pathways, MAC, regulators
- Th1, Th2, Th17, Tfh and Treg
- Cytokines: the table to know
- Type I interferons (α, β)
- Direct and indirect Coombs test
- Immunofluorescence and the ANA test
In physiology
Why it happens
- Apoptosis: the intrinsic and extrinsic pathways
- When leukocytes injure tissue: proteases, oxidants and NETs
- Innate and adaptive immunity: overview
- Immunoglobulins (antibodies)
- Glomerulus and the filtration barrier: podocytes, mesangium, JGA
What it is
A chronic autoimmune disease in which autoantibodies and immune complexes inflame many organs, mainly skin, joints, kidneys, blood cells, serous membranes and the nervous system. It runs in flares and remissions.
Who gets it
Much more common in women, especially of childbearing age (about nine women per man is often quoted), and often more frequent and severe in people of African, Hispanic and Indigenous ancestry. In a Buenos Aires, Argentina, health-insurance population, incidence was 6.3 per 100,000 person-years and prevalence 58.6 per 100,000 in 2009.
Causes
- Genetic susceptibility (several immune genes, including complement deficiencies)
- Hormonal factors: oestrogen
- Environmental triggers: ultraviolet light, infections (for example Epstein-Barr virus), smoking
- Some drugs cause a separate, usually milder drug-induced lupus
Risk factors
- Female sex, ages 15 to 45
- African, Hispanic, Asian or Indigenous ancestry
- Family history of lupus or other autoimmune disease
- Sun exposure
- Smoking
Pathophysiology
Faulty clearance of dying cells exposes nuclear antigens; loss of tolerance leads to autoantibodies such as ANA and anti-dsDNA. Immune complexes deposit in the kidney, skin and vessels and activate complement (type III hypersensitivity). Some antibodies attack blood cells directly (type II). Interferon-driven inflammation sustains the disease.
Classification
- Classification criteria (2019 EULAR/ACR): a positive ANA is the entry criterion, then weighted clinical and immunological items; criteria are for research and support, not replace, diagnosis
- Lupus nephritis classes I to VI on kidney biopsy
- Cutaneous forms: acute (malar), subacute and chronic (discoid)
- Drug-induced lupus and neonatal lupus
Symptoms and signs
- Fatigue, fever and weight loss
- Malar (butterfly) rash sparing the nasolabial folds; photosensitivity
- Discoid lesions, painless oral ulcers and non-scarring hair loss
- Symmetric, non-erosive arthritis of the small joints of the hands and wrists
- Pleuritic chest pain (pleurisy) or pericarditis
- Foamy urine, oedema or high blood pressure from nephritis
- Raynaud phenomenon
Diagnosis
- Clinical
- Diagnosis rests on a compatible pattern of features in several organs plus supportive antibodies; clinicians actively look for kidney, blood and neurological involvement.
- Tests
- ANA (very sensitive; a negative result makes lupus unlikely), anti-dsDNA and anti-Smith (specific), low complement C3 and C4, antiphospholipid antibodies, blood count, creatinine, urinalysis and urine protein. Kidney biopsy classifies nephritis.
- Imaging
- Not diagnostic; echocardiography, chest X-ray or CT, and brain MRI are used when heart, lung or nervous system involvement is suspected.
Differential diagnosis
- Rheumatoid arthritis
- Drug-induced lupus
- Other connective tissue diseases (Sjögren, systemic sclerosis, mixed connective tissue disease)
- Viral infections (parvovirus B19, HIV, hepatitis)
- Rosacea or dermatomyositis (facial rash)
- Fibromyalgia (fatigue and pain with a positive low-titre ANA)
Goal of treatment
Achieve remission or low disease activity, prevent flares and organ damage (especially to the kidneys), keep steroid exposure as low as possible and reduce cardiovascular and infection risk.
Treatment
- Medical
- Antimalarial agents are recommended for nearly all patients; they reduce flares and improve survival, with regular eye screening.
- Medical
- Glucocorticoids for flares, tapered to the lowest dose possible; steroid-sparing immunosuppressants for organ involvement.
- Medical
- Lupus nephritis and severe disease: induction and maintenance immunosuppression, and biologic agents in selected cases.
- Lifestyle
- Sun protection, stopping smoking, vaccination and planning pregnancy during quiet disease.
- Follow-up
- Regular blood count, kidney function, urine protein, complement and anti-dsDNA, plus cardiovascular risk and bone health review.
Drugs for this condition
Complications
- Chronic kidney disease and kidney failure
- Accelerated atherosclerosis and cardiovascular events
- Serious infections from disease and treatment
- Antiphospholipid syndrome with thrombosis and pregnancy loss
- Neonatal lupus and congenital heart block (anti-Ro antibodies)
- Steroid side effects: osteoporosis, avascular necrosis, diabetes
Prognosis
Survival has improved greatly with earlier diagnosis and modern treatment. Outcomes are worse with kidney or nervous system involvement; infection and cardiovascular disease are major late causes of death.
Prevention
- Sun protection to reduce skin and systemic flares
- Vaccination (inactivated vaccines) before strong immunosuppression when possible
- Preconception counselling and close follow-up in pregnancy
Test yourself
Think of the answer, then tap the question to see it.
Which antibody test is most sensitive for SLE, and which are most specific?
ANA is the most sensitive (screening). Anti-dsDNA and anti-Smith are the most specific; anti-dsDNA levels often track nephritis activity.
How does the malar rash of lupus differ from rosacea or seborrhoeic dermatitis?
It is a photosensitive butterfly rash over the cheeks and nasal bridge that classically spares the nasolabial folds.
Which lab pattern suggests active lupus nephritis?
Rising anti-dsDNA with low C3 and C4, plus proteinuria, haematuria or red cell casts and a rising creatinine; biopsy confirms the class.
Which antibody is typical of drug-induced lupus?
Anti-histone antibodies; kidney and nervous system disease are rare and the illness usually resolves when the drug is stopped.
Which maternal antibody can cause congenital heart block?
Anti-Ro (SSA), and less often anti-La (SSB), which cross the placenta and damage the fetal conduction system (neonatal lupus).
Related conditions
- Rheumatoid arthritis
- Preeclampsia
- Chronic kidney disease
- Avascular necrosis of the femoral head
- Infective endocarditis
- Acute pericarditis
- Interstitial lung disease
- Rheumatoid arthritis of the hand and wrist
Educational information, not medical advice. For any symptom, see a health professional.
Sources: Systemic Lupus Erythematosus (StatPearls (NCBI Bookshelf), 2026); Global excellence in rheumatology in Latin America: The case of systemic lupus erythematosus (Frontiers in medicine, 2022) · adapted, CC BY 4.0.
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Representative model, for educational purposes only.
