Lupus Erythematosus: Systemic with Skin Manifestations

SLE Basics - Lupus Unmasked

• Definition: Systemic Lupus Erythematosus (SLE) is a chronic, relapsing-remitting, multisystem autoimmune disease characterized by diverse mucocutaneous and systemic manifestations.
• Key Pathogenesis:
  • Autoantibody formation: ANA (most sensitive), anti-dsDNA (correlates with disease activity, nephritis), anti-Sm (highly specific).
  • Immune complex deposition: Type III Hypersensitivity leading to vasculitis and tissue damage.
  • Complement activation: ↓C3, ↓C4.
  • Genetic predisposition: Associated with HLA-DR2, HLA-DR3.
  • Environmental triggers: UV light exposure, certain drugs (e.g., hydralazine, procainamide, isoniazid), infections.
• Epidemiology: Affects predominantly women of childbearing age (Female:Male ratio ≈ 9:1).

⭐ Anti-Sm (Smith antigen) antibody is highly specific for SLE, though less sensitive than ANA.

Skin Deep Lupus - Rash Decisions

• Gilliam Classification of Cutaneous LE (CLE):
  • Acute Cutaneous LE (ACLE):
    • Localized: Malar "butterfly" rash (spares nasolabial folds).
    • Generalized: Widespread maculopapular rash on sun-exposed areas.
    • Strongly associated with systemic disease activity.
  • Subacute Cutaneous LE (SCLE):
    • Highly photosensitive, non-scarring, non-indurated lesions.
    • Forms: Papulosquamous (psoriasiform) or annular/polycyclic.
    • Often Anti-Ro/SSA positive; can be drug-induced (e.g., HCTZ, terbinafine).
  • Chronic Cutaneous LE (CCLE):
    • Discoid LE (DLE) - most common CCLE:
      • Erythematous indurated plaques, adherent scale, follicular plugging.
      • Leads to atrophy, scarring, dyspigmentation.
      • Sites: Face, scalp (scarring alopecia), ears.
      • 📌 DLE: A SCAR (Atrophy, Scale, Central hypopigmentation/depigmentation, Active erythematous border, Rim of hyperpigmentation, Follicular plugging).
    • Other forms: LE profundus (panniculitis), Chilblain lupus, Tumid lupus.
• Other Mucocutaneous Manifestations:
  • Painless oral/nasal ulcers.
  • Non-scarring diffuse alopecia ("lupus hair").
  • Raynaud's phenomenon, Livedo reticularis, cutaneous vasculitis.

⭐ The malar rash in ACLE characteristically spares the nasolabial folds, a key diagnostic clue.

Spotting SLE - Lupus Detectives

• EULAR/ACR Criteria (2019):
  • Entry: ANA titer ≥1:80.
  • Score ≥10 for classification.
  • Mucocutaneous: Non-scarring alopecia (2), Oral ulcers (2), SCLE/DLE (4), Acute cutaneous lupus (6).
• Investigations:

  • Skin Biopsy (lesional): Interface dermatitis, liquefaction degeneration, epidermal atrophy, thickened BM (PAS+).

  • DIF/LBT: Granular IgG, IgM, C3 at DEJ. Lesional (>90%), sun-exposed non-lesional (SLE ~50-70%).

  • Serology: ANA (>95%), Anti-dsDNA (activity, nephritis), Anti-Sm (specific). 📌 'S'm 'S'pecific, d'S'dna 'S'evere. Low C3/C4.

    • Others: Anti-Ro/SSA (SCLE, neonatal lupus), Anti-La/SSB, Anti-U1 RNP, Anti-histone (drug-induced).
• Diagnostic Flow (Simplified):

⭐ A positive Lupus Band Test (IgG at DEJ) in sun-exposed, non-lesional skin is highly suggestive of systemic lupus erythematosus.

Managing the Wolf - Skin Shield

• General: Photoprotection (broad-spectrum sunscreen SPF $ \ge 30-50 $, protective clothing, sun avoidance), Smoking cessation, Vitamin D.
• Topical (CLE):
  • Corticosteroids: Potent (clobetasol - DLE); mid-potency. Risk: atrophy.
  • Calcineurin inhibitors: Tacrolimus, pimecrolimus (face, steroid-sparing).
• Systemic (Severe CLE/SLE):
  • Antimalarials: HCQ ($ \le 5 \text{ mg/kg/day} $ actual body weight) or Chloroquine. 1st line CLE & mild SLE. Ophthalmology screen (retinal toxicity).
  • Systemic Corticosteroids: Prednisolone for flares/severe disease, tapered.
  • Immunosuppressants: MTX, AZA, MMF (refractory CLE, steroid-sparing).
  • Biologics: Belimumab, Rituximab, Anifrolumab (refractory/severe SLE).
  • Other: Dapsone, Thalidomide (refractory DLE, teratogenicity/neuropathy risk).

⭐ Hydroxychloroquine is a cornerstone in managing cutaneous lupus; requires baseline and annual ophthalmological screening after 5 years (or sooner with risk factors).

High‑Yield Points - ⚡ Biggest Takeaways

• Malar rash: Classic photosensitive "butterfly" erythema, spares nasolabial folds.
• Discoid Lupus (DLE): Erythematous plaques, scale, follicular plugging; causes scarring alopecia, dyspigmentation.
• Subacute Cutaneous LE (SCLE): Highly photosensitive, non-scarring; strong anti-Ro/SSA association.
• Lupus profundus: Deep, firm nodules (panniculitis); may result in lipoatrophy.
• Oral ulcers: Typically painless, common on palate/buccal mucosa.
• Key Serology: ANA >95%; anti-dsDNA & anti-Sm highly specific.
• Drug-induced SLE: Anti-histone Ab positive; skin signs less common.