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Musculoskeletal · Clinical Topics

Systemic Lupus Erythematosus

⏱️ 30 mins read 📖 Clinical Topics 🎯 MLA Relevance: High

Systemic Lupus Erythematosus (SLE) is a multisystem, chronic autoimmune disease characterised by the production of various autoantibodies, most notably anti-nuclear antibodies (ANA). It follows a relapsing-remitting course and can affect almost any organ system, including the skin, joints, kidneys, and heart. Management focuses on hydroxychloroquine and immunosuppression.

📌 Learning Objectives

  • Describe the epidemiology and aetiology of Systemic Lupus Erythematosus (SLE).
  • Identify the key clinical features and diagnostic criteria for SLE.
  • Explain the basic immunological mechanisms underlying SLE pathogenesis.
  • Outline the serological markers used in the diagnosis and monitoring of SLE.
  • Formulate a management plan for patients with varying severities of SLE and its complications.
  • Recognise the importance of long-term monitoring and patient education in SLE.

📋 Overview

SLE predominantly affects women of childbearing age (9:1 ratio) and is more common and severe in individuals of Afro-Caribbean and Asian descent. It is the 'great mimicker' due to its vast range of presentations. Common features include a malar (butterfly) rash, photosensitivity, non-erosive arthritis, and constitutional symptoms like fatigue and fever. The most serious complications involve the kidneys (Lupus Nephritis) and the central nervous system. Diagnosis is clinical and supported by serology, using the ACR or SLICC criteria. Serologically, ANA is highly sensitive (>95%), but anti-dsDNA and anti-Smith antibodies are highly specific. Low complement levels (C3, C4) indicate disease activity. Management is tailored to organ involvement, with Hydroxychloroquine recommended for all patients to reduce flares and improve long-term survival.

🔬 Basic Science

The pathogenesis of SLE involves a failure of self-tolerance and defective clearance of apoptotic cells. This leads to an accumulation of nuclear antigens (like DNA and histones). B-cells produce autoantibodies against these antigens, forming immune complexes. These complexes deposit in various tissues (Type III hypersensitivity), activating the complement cascade and causing inflammatory tissue damage. Additionally, Type I interferons (IFN-α) play a central role in driving the immune response. Genetic predisposition (including HLA-DR2/DR3) and environmental triggers like UV light (which induces keratinocyte apoptosis) are key factors.

🏥 Clinical Relevance

Symptoms are broad: 1. Musculoskeletal: Symmetrical small-joint arthralgia/arthritis (non-erosive). 2. Dermatological: Malar rash, discoid lupus, alopecia. 3. Renal: Proteinuria, haematuria (Lupus Nephritis Class I-VI). 4. Haematological: Anaemia of chronic disease, leucopenia, thrombocytopenia. 5. Serositis: Pleurisy, pericarditis. 6. Neurological: Seizures, psychosis. 7. Cardiovascular: Increased risk of atherosclerosis and Libman-Sacks endocarditis. Lupus in pregnancy is associated with flares and neonatal lupus (congenital heart block due to anti-Ro/La antibodies).

🧪 Investigations

- Bloods: ANA (Screen), Anti-dsDNA (specific/monitoring), Anti-Smith (very specific), ESR (usually high), CRP (often normal unless infection or serositis), FBC, C3/C4.
- Urine: Urinalysis and protein-creatinine ratio (ACR) to screen for nephritis.
- Imaging: CXR (pleural effusion), Echocardiogram (pericarditis/valval disease).
- Special: Renal biopsy if proteinuria >0.5g/day to determine the class of nephritis.

💊 Management

General: Sun protection (high SPF). Medical: Hydroxychloroquine (200-400mg daily) is standard. For mild disease: NSAIDs and low-dose steroids. For moderate/severe flares: High-dose oral or IV steroids (Prednisolone). Steroid-sparing agents: Azathioprine, Methotrexate, or Mycophenolate Mofetil (especially for lupus nephritis). Biologics: Belimumab or Rituximab for resistant disease. Anticoagulation is required if there is co-existing Antiphospholipid Syndrome.

Revision Resources – expand the sections below for high-yield notes, exam pearls, key facts and further reading.

🎯 MLA High-Yield Notes & Quick Revision ⌄
ANA negative SLE is extremely rare (<1%). If an ANA is negative, reconsider the diagnosis. Classic mnemonic for SLE features: SOAP BRAIN MD (Serositis, Oral ulcers, Arthritis, Photosensitivity, Blood disorders, Renal, ANA, Immunologic, Neurologic, Malar rash, Discoid rash).
Chronic fatigue and systemic illness Arthritis and arthralgia Skin rashes and photosensitivity Renal impairment (proteinuria, haematuria) Pleuritic chest pain Neurological symptoms (seizures, psychosis)
  • SLE is a chronic, multisystem autoimmune disease.
  • Predominantly affects young women, often with a relapsing-remitting course.
  • Key features: malar rash, photosensitivity, arthritis, serositis, renal involvement.
  • Diagnosis relies on clinical criteria and serology (ANA, anti-dsDNA, anti-Smith).
  • Lupus nephritis is a serious complication, requiring close monitoring.
  • Low C3/C4 indicates active disease.
⭐ Exam Pearls ⌄
⭐ High Yield
SLE is a multisystem autoimmune disease predominantly affecting women of childbearing age (9:1 ratio).
ANA is highly sensitive for SLE, but anti-dsDNA and anti-Smith antibodies are highly specific.
Malar rash (sparing nasolabial folds) and photosensitivity are characteristic dermatological features.
Lupus nephritis is a major cause of morbidity and mortality, requiring close monitoring (urine ACR, renal biopsy).
Low C3/C4 complement levels indicate active disease or flare.
Hydroxychloroquine is recommended for all SLE patients to reduce flares and improve outcomes.
Drug-induced lupus is associated with anti-histone antibodies and often resolves upon drug cessation.
Lupus in pregnancy can lead to flares and neonatal lupus (congenital heart block due to anti-Ro/La).
💡 Clinical Pearl
Nephrotic Syndrome: Lupus nephritis (especially Class V) can present with nephrotic-range proteinuria, oedema, and hypoalbuminemia.
Nephritic Syndrome: Lupus nephritis (e.g., Class III/IV) can present with haematuria, proteinuria, hypertension, and acute kidney injury, characteristic of nephritic syndrome.
Pericarditis: Serositis, including pericarditis, is a common manifestation of SLE, presenting with chest pain and often a pericardial rub.
Acute Kidney Injury: Severe lupus nephritis can lead to rapid deterioration of renal function, presenting as AKI.
⚠️ Exam Tip — Common Mistakes
Assuming a negative ANA rules out SLE entirely (it's rare but possible).
Not considering drug-induced lupus in new-onset SLE-like symptoms, especially with relevant drug history.
Failing to monitor for lupus nephritis with regular urine ACRs.
Underestimating the importance of hydroxychloroquine in all SLE patients, regardless of disease severity.
Confusing the malar rash of SLE with rosacea or other facial rashes (SLE spares nasolabial folds).
Not considering Antiphospholipid Syndrome in SLE patients with thrombotic events or recurrent miscarriages.
🔑 Key Facts ⌄
Multisystem autoimmune disease; 90% of patients are female.
Hallmark: Malar rash (spares nasolabial folds), photosensitivity, and oral ulcers.
Serology: Positive ANA (sensitive), Anti-dsDNA and Anti-Smith (specific).
Lupus nephritis is a major cause of morbidity (monitored via urine ACR).
Low C3/C4 levels indicate an active flare.
Hydroxychloroquine is first-line for all SLE patients.
Drug-induced lupus (e.g., Hydralazine, Isoniazid) typically has anti-histone antibodies.
🔗 Related Topics ⌄
💧 Nephrotic Syndrome Renal → 💧 Nephritic Syndrome Renal → 💧 Acute Kidney Injury Renal → ❤️ Pericarditis Cardiovascular → 💧 Chronic Kidney Disease Renal →
📚 References ⌄
  1. British Society for Rheumatology SLE Guideline
  2. NICE CKS - SLE
  3. Kumar & Clark

Further Resources

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