Systemic lupus erythematosus

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Definition

  • Multisystem inflammatory disorder of unknown etiology

ACR Classification Criteria

4 or more of the following (4RASHES mnemonic)

  • Four dermatologic manifestations
    • Malar rash: spares nasolabial folds
    • Discoid rash: erythemaous plaques/patches
    • Photosensitivity: rash, not sunburn
    • Mucocutaneous ulcers: oropharynx or nasopharynx, often painless
  • Renal disorder
    • Proteinuria >0.5g/d or 3+
    • Any cellular or granular casts
  • Arthritis: non-erosive involving 2 or more joints
  • Serositis: pleuritis or pericarditis
  • Hematologic disorder
    • Hemolytic anemia
    • Leukopenia
    • Lymphopenia: most important
    • Thrombocytopenia
  • Neurological excitability
    • Seizures
    • Psychosis
  • Serology (non-ANA)
    • Anti-dsDNA antibodies
    • Anti-Sm antibodies
    • Anti-phospholipid antibodies
  • Serology (ANA): most sensitive finding (~98%)

Clinical Manifestations

  • See above criteria
  • Fevers and other constitutional symptoms
  • Any other non-specific rash, even if not in criteria
    • Discoid rash forms scars
  • Alopecia, either discrete or global

Investigations

  • Most important tests
    • CBC for lymphopenia & other hematologic abnormalities
    • Urinalysis for active sediment
  • Serology
    • ANA most sensitive, anti-Smith and anti-dsDNA are most specific
    • APLA
    • Can be either seroconcordant or -discordant for dsDNA, C3/C4, ESR/CRP during flares

Management

Acute

Chronic

  • Hydroxychloroquine
    • Load with 400-600 mg TDD split BID for 1-3 months
    • Step down to 6.75 mg/kg maintenance
    • Needs Ophthalmology follow-up for rare macular side effect
    • Best for skin
  • Azathioprine as steroid-sparing agent