Lupus Erythematosus: Cutaneous Forms

CLE Overview - Lupus's Skin Game

Cutaneous Lupus Erythematosus (CLE) presents with diverse skin manifestations, often independent of systemic lupus erythematosus (SLE).

• Classification:
  • Acute Cutaneous LE (ACLE)
  • Subacute Cutaneous LE (SCLE)
  • Chronic Cutaneous LE (CCLE)
    • Discoid LE (DLE) is the most common CCLE.

⭐ SCLE is strongly associated with anti-Ro/SSA antibodies (found in ~70-90% of cases).

ACLE - Butterfly's Kiss

• Acute Cutaneous Lupus Erythematosus (ACLE).
• Classic Sign: Malar "butterfly" rash - erythematous, edematous eruption on cheeks & nasal bridge.
• Distribution: Strongly photosensitive; occurs in sun-exposed areas.
• Systemic Link: High association with active Systemic Lupus Erythematosus (SLE).
• Outcome: Usually heals without scarring; post-inflammatory pigment changes possible.

⭐ Often the first manifestation of SLE or signals a disease flare, especially with systemic symptoms like fever or arthralgia.

SCLE - Sun's Scaly Souvenir

• Photosensitive, typically non-scarring eruption on sun-exposed sites (V-neck, arms, back). 📌 Sun's Scaly Souvenir!
• Two main types:
  • Annular/polycyclic (raised red borders, central clearing)
  • Papulosquamous (scaly plaques, resembles psoriasis/eczema)
• Antibodies: Anti-Ro/SSA ( >70-90% ), Anti-La/SSB ( ~30-50% ).
• ~50% fulfill criteria for mild SLE.
• Drug-induced SCLE is common (e.g., HCTZ, PPIs, terbinafine).

⭐ Strong Anti-Ro/SSA positivity ( >70% ); risk of neonatal lupus if mother is positive.

DLE/CCLE - Discoid Damage Drama

• Most common Chronic Cutaneous LE (CCLE).
• Lesions: Well-demarcated erythematous plaques; adherent scale, follicular plugging, central atrophy, scarring alopecia.
  • Sun-exposed areas: face, scalp, ears.
• 📌 Mnemonic "SCAR": Scarring alopecia, Central atrophy, Adherent scale, Rim of erythema.
• Low risk of systemic LE progression (~5-10%).
• Chronic lesions: risk of Squamous Cell Carcinoma (SCC).

⭐ "Carpet tack" sign: horny plugs on undersurface of lifted scale, classic for DLE/CCLE an exam favourite finding indicating follicular plugging when the scale is removed from a lesion of discoid lupus erythematosus (DLE).

Rarer CLE Forms - Lupus's Odd Bunch

• Tumid Lupus Erythematosus (TLE)
  • Urticarial plaques, minimal epidermal change, dermal mucin.
  • Excellent prognosis, responds well to antimalarials.
  • Photosensitive.
• Lupus Erythematosus Panniculitis (LEP)/Lupus Profundus
  • Deep, firm nodules; may ulcerate, cause lipoatrophy ("doughnut-like" depressions).
  • Often on proximal limbs, face.
• Chilblain Lupus Erythematosus (CHLE)
  • Purple, painful plaques on acral sites (fingers, toes, nose, ears) in cold, damp weather.
  • May coexist with other LE forms.

⭐ Lupus Panniculitis can precede systemic lupus erythematosus (SLE) diagnosis by years or occur with active SLE or DLE (Discoid Lupus Erythematosus).

CLE Diagnostics - Unmasking Lupus

• Clinical: Photosensitive rash, discoid lesions, alopecia.
• Histopathology (HPE): Interface dermatitis, follicular plugging, liquefaction degeneration.
• Direct Immunofluorescence (DIF): Lupus Band Test (LBT) - IgG, IgM, C3 at dermoepidermal junction (DEJ).
  • LBT: +ve in lesional skin (90%), sun-exposed non-lesional (70-80%), non-sun-exposed non-lesional (50%).
• Serology: ANA (sensitive), Anti-dsDNA, Anti-Sm (specific for SLE), Anti-Ro (SSA), Anti-La (SSB).

⭐ Lupus Band Test: Granular deposition of IgG and C3 at the DEJ is characteristic. Positive in >90% of lesional skin in DLE.

CLE Management - Skin Shield Strategy

• Core: Sun protection (SPF >30 UVA/UVB), smoking cessation.
• Topical:
  • Corticosteroids (potent/mid-potency).
  • Calcineurin inhibitors (face, flexures).
• Systemic (widespread/refractory):
  • Antimalarials (Hydroxychloroquine - HCQ).
  • Immunosuppressants (MTX, AZA, MMF).
  • Retinoids, Dapsone.

⭐ Hydroxychloroquine (HCQ) mandates baseline and annual eye exams due to risk of retinal toxicity.

High‑Yield Points - ⚡ Biggest Takeaways

• Discoid Lupus Erythematosus (DLE) is the most common chronic form, presenting with well-demarcated plaques, adherent scale, follicular plugging, and atrophic scarring.
• Subacute Cutaneous Lupus Erythematosus (SCLE) features photosensitive, non-scarring, annular or papulosquamous lesions, often anti-Ro/SSA positive.
• Acute Cutaneous Lupus Erythematosus (ACLE) typically manifests as a malar rash ("butterfly rash") and strongly correlates with active Systemic Lupus Erythematosus (SLE).
• Lupus profundus involves deep, tender nodules leading to lipoatrophy.
• Direct Immunofluorescence (DIF) of lesional skin showing a "lupus band" (IgG, IgM, C3 at dermoepidermal junction) is diagnostic.
• Key management includes strict sun protection, topical/intralesional corticosteroids, and hydroxychloroquine.
• Drug-induced SCLE is commonly associated with drugs like terbinafine, hydrochlorothiazide, and PPIs.