Systemic Lupus Erythematosus

SLE Introduction & Pathophysiology - The Immune Betrayal

• Definition: Chronic, multisystem autoimmune inflammatory disease.
• Epidemiology: F:M ratio ~9:1; peak onset 15-45 years.
• Predisposition: Genetic (HLA-DR2, HLA-DR3), environmental triggers (UV, drugs, infections).
• Pathophysiology: Autoimmunity due to loss of self-tolerance.
  • Autoantibody production: ANA (screening), anti-dsDNA & anti-Sm (specific).
  • Immune complex deposition (Type III hypersensitivity) & Type II cytotoxic reactions.
  • Complement activation leading to tissue inflammation & damage.

⭐ SLE is characterized by the loss of self-tolerance and production of autoantibodies against nuclear antigens.

SLE Clinical Spectrum - Rash to Renal

• Constitutional: Fever, fatigue, weight loss.
• Mucocutaneous:
  • Malar rash (spares nasolabial folds).
  • Discoid lupus.
  • Photosensitivity.
  • Oral ulcers (painless).
  • Alopecia (non-scarring).
• Musculoskeletal: Non-erosive arthritis (Jaccoud's arthropathy), arthralgia, myalgia.
• Serositis: Pleuritis, pericarditis.
• Hematological: Anemia (of chronic disease, hemolytic), leukopenia, lymphopenia, thrombocytopenia.
• Renal (Lupus Nephritis): Proteinuria, hematuria. Classes I-VI (biopsy-based).
  • Class I: Minimal mesangial LN
  • Class II: Mesangial proliferative LN
  • Class III: Focal LN (<50% glomeruli)
  • Class IV: Diffuse LN (>50% glomeruli) - most common & severe
  • Class V: Membranous LN
  • Class VI: Advanced sclerosing LN (>90% sclerosed glomeruli)
• Neuropsychiatric (NPSLE): Seizures, psychosis, cognitive dysfunction, stroke.
• Cardiovascular: Libman-Sacks endocarditis (verrucous, non-bacterial, on mitral/aortic valves).

⭐ Malar rash (butterfly rash) characteristically spares the nasolabial folds.

📌 SOAP BRAIN MD (Mnemonic for SLE criteria - not exhaustive for clinical spectrum but helpful)

• Serositis
• Oral ulcers
• Arthritis
• Photosensitivity
• Blood disorders
• Renal disorder
• ANA positive
• Immunologic disorder (anti-dsDNA, anti-Sm, antiphospholipid Ab)
• Neurologic disorder
• Malar rash
• Discoid rash

SLE Diagnosis & Labs - Unmasking SLE

• 2019 EULAR/ACR Classification Criteria:
  • Entry criterion: ANA $\ge$ 1:80.
  • Additive weighted criteria from clinical & immunological domains; score $>$ 10 points needed for classification.

Key Autoantibodies in SLE:

*   ↓C3, ↓C4 (complement consumption, active disease)
*   ↑ESR (inflammation, non-specific)

⭐ Anti-Sm antibody is the most specific antibody for SLE.

SLE Management & Complications - Calming the Storm

Goals: Achieve remission, prevent flares & organ damage.

• General Measures: Sun protection, lifestyle. HCQ for ALL (unless contraindicated).

  ⭐ Hydroxychloroquine (HCQ) is recommended for all SLE patients unless contraindicated, as it reduces flares and improves survival.

• Pharmacological Therapy (Severity-based):
  • Mild: NSAIDs, low-dose corticosteroids.
  • Moderate/Severe: Corticosteroids (high-dose/pulse), Immunosuppressants (Mycophenolate Mofetil - MMF, Azathioprine - AZA, Cyclophosphamide - CYC), Biologics (Belimumab for refractory).
• Lupus Nephritis Management:
  • Induction: MMF or CYC + high-dose steroids.
  • Maintenance: MMF or AZA.
• Drug-Induced Lupus: 📌 Hydralazine, Procainamide, Isoniazid (HPI). Anti-histone Abs characteristic.
• SLE & Pregnancy: HCQ safe. Plan conception during remission (≥6 months).
• Key Complications: Lupus Nephritis, accelerated atherosclerosis, infections, osteoporosis, AVN.

Treatment Algorithm:

High-Yield Points - ⚡ Biggest Takeaways

• SLE is a multisystem autoimmune disease predominantly affecting young females.
• ANA is a sensitive screening test; anti-dsDNA and anti-Sm antibodies are highly specific.
• Characteristic skin manifestations include malar rash (butterfly rash) and discoid rash.
• Lupus nephritis is a major cause of morbidity; renal biopsy is crucial for prognosis and management.
• Drug-induced lupus (e.g., hydralazine, procainamide) is often associated with anti-histone antibodies.
• Coexisting Antiphospholipid Syndrome (APS) significantly ↑ risk of thrombosis and recurrent fetal loss.
• Hydroxychloroquine (HCQ) is a cornerstone for long-term management in most patients.