🔑 Key Learning

  • Multisystem autoimmune disease caused by immune complex deposition (type III hypersensitivity)
  • Classic signs: malar rash, arthralgia, fatigue, lupus nephritis
  • Antibodies: Anti-dsDNA and anti-Smith highly specific
  • Drug-induced lupus = anti-histone +ve, ANA +ve, dsDNA -ve
    • Drugs: Procainmide, hydralazine
  • Neonatal lupus risk in pregnancy → congenital heart block

🧬 Pathophysiology

  • Type III hypersensitivity: immune complex (Ag:Ab) deposition
    • Genetic association: HLA-DR3, DR2, B8
  • Multisystem involvement → tissue inflammation and damage

📊 Epidemiology

  • 1 in 1000 in the UK
  • Female:Male = 9:1
  • Most common in African-Caribbean populations
  • Age of onset: 20–40 years

👀 Clinical Features

General

  • Fever, fatigue, weight loss, lymphadenopathy

🧴 Dermatological

  • Photosensitive rash (malar/butterfly, sparing nasolabial folds)
  • Discoid rash
  • Livedo reticularis
SLE. Malar rash. Doktorinternet, CC BY-SA 4.0, via Wikimedia Commons

🦴 MSK

  • Arthralgia, non-erosive arthritis

❤️ Cardiovascular

  • Pericarditis, myocarditis

🫁 Respiratory

  • Pleuritis, fibrosing alveolitis

🧠 Neuro

  • Seizures, psychosis

🧬 Renal

  • Lupus nephritis (e.g. diffuse proliferative GN with ‘wire loop’ lesions)

👶 Complications in Pregnancy

  • Maternal anti-Ro/La antibodies → neonatal lupus
  • Risk of congenital heart block

🧪 Investigations

Autoantibodies

  • ANA – 95% sensitive
  • Anti-dsDNA – 95% specific
  • Anti-Smith (Sm) – 98% specific
  • Anti-Ro / Anti-La (also associated with neonatal lupus)

Monitoring Disease Activity

  • Anti-dsDNA titres
  • Low complement (C3, C4) = active disease
  • ESR raised, CRP normal (↑CRP suggests infection)

💊 Management

  • Mild (skin/joints): Hydroxychloroquine ± NSAIDs
  • Moderate (serositis, cytopaenias): Add oral steroids ± immunosuppressants
  • Severe (renal, CNS): IV steroids ± cyclophosphamide, mycophenolate
  • Sun protection + regular monitoring
  • Consider anticoagulation if co-existent APS

💊 Drug-Induced Lupus (DIL)

🧬 Causes

  • Procainamide, Hydralazine, Isoniazid, Minocycline, Phenytoin

👀 Features

  • Fever, malar rash, arthralgia, pleurisy

🧪 Antibodies

  • ANA positive
  • Anti-histone antibodies (90%)
  • Anti-dsDNA negative

💊 Management

  • Stop the causative drug

🧴 Discoid Lupus Erythematosus (DLE)

👀 Features

  • Scaly, anular lesions on face, scalp, ears
  • Carpet tack sign – follicular keratin plugs
  • Scarring alopecia common
  • Photosensitive
Discoid lupus. Scarring alopecia. Mohammad2018, CC BY-SA 40 >, via Wikimedia Commons

💊 Management

  • 1st line: Topical corticosteroids
  • 2nd line: Hydroxychloroquine
  • Advise sun protection

📝 Exam Clues & Clinchers

  • 30F with photosensitive malar rash + arthralgia + fatigue → SLE
  • Suspected SLE? Check anti-dsDNA and anti-smith antibodies
  • Photosensitive rash + scarring alopecia → Discoid lupus
  • ANA + anti-histone + new drug history → Drug-induced lupus