Pemphigus Foliaceus

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Overview & Pathogenesis - Leafy Skin Split

  • Pemphigus Foliaceus (PF): A chronic, superficial autoimmune blistering disease affecting the skin.
  • Core Pathogenesis:
    • Autoantibodies (IgG, often IgG4) target Desmoglein 1 (DSG1), a keratinocyte adhesion molecule.
    • Leads to acantholysis (separation of keratinocytes).
    • Results in intraepidermal split within the superficial epidermis (subcorneal or upper granular layer).
    • 📌 Foliaceus = Fragile, Flakes (superficial, "leaf-like" scales).

⭐ Pemphigus foliaceus is the most common autoimmune blistering disease in certain endemic regions of Brazil (Fogo Selvagem).

Clinical Features - Scaly Crusty Rash

  • Morphology:
    • Superficial, fragile blisters (often ruptured, rarely seen intact).
    • Leads to scaly, crusted erosions.
    • Characteristic "cornflake" like scales.
    • Well-demarcated lesions.
  • Distribution:
    • Primarily affects seborrheic areas:
      • Scalp (often initial site)
      • Face (malar region, forehead)
      • Chest (V-area)
      • Upper back
  • Mucous Membranes: Typically spared (key differentiator from Pemphigus Vulgaris).
  • Symptoms:
    • Pruritus (itching) is common and can be intense.
    • Burning sensation may occur.
  • Variants:
    • Fogo Selvagem (Endemic Pemphigus Foliaceus): Brazil, rural areas.
    • Pemphigus Erythematosus (Senear-Usher Syndrome): Overlap with lupus erythematosus; facial lesions, +ANA.

⭐ Nikolsky sign is often positive in Pemphigus Foliaceus, though blisters are very superficial.

Diagnosis - Spotting the Split

Key investigations aim to identify the specific level of epidermal split and the presence of pathogenic autoantibodies:

  • Skin Biopsy: Crucial for diagnosis.
    • Lesional skin (Histopathology - HPE): Shows characteristic subcorneal or intragranular acantholysis (epidermal cell separation).
    • Perilesional skin (Direct Immunofluorescence - DIF): Gold standard; reveals intercellular IgG and C3 deposition in the superficial epidermis, creating a "chicken-wire" pattern.

      ⭐ Direct immunofluorescence showing intercellular IgG deposition in the superficial epidermis is key for diagnosis.

  • Serum Tests:
    • Indirect Immunofluorescence (IIF): Detects circulating anti-Desmoglein 1 (anti-DSG1) IgG autoantibodies.
    • ELISA (Enzyme-Linked Immunosorbent Assay): Confirms presence and quantifies anti-DSG1 antibodies; useful for diagnosis and monitoring disease activity.
  • Tzanck Smear:
    • Rapid test showing acantholytic cells (Tzanck cells); less specific but can be suggestive.

Direct immunofluorescence in Pemphigus Foliaceus

DDx & Management - Calm the Chaos

Differential Diagnosis:

ConditionKey Differentiators (vs PF)
ImpetigoBacterial, superficial, honey-colored crusts
Subcorneal Pustular DermatosisSterile pustules, chronic, annular/serpiginous
Dermatitis HerpetiformisIntense pruritus, grouped vesicles, IgA at DEJ
Pemphigus VulgarisDeeper intraepidermal split, oral lesions common
Seborrheic Dermatitis (severe)Greasy scales, scalp/face/chest distribution

⭐ Unlike Pemphigus Vulgaris, Pemphigus Foliaceus generally has a better prognosis and lower mortality rate.

High‑Yield Points - ⚡ Biggest Takeaways

  • Superficial autoimmune blistering disease; targets Desmoglein 1 (DSG1).
  • Histopathology: subcorneal split with acantholytic cells in the upper epidermis.
  • Clinical: crusted, scaly erosions on seborrheic areas (face, scalp, chest); mucosa is spared.
  • Nikolsky sign is typically positive.
  • DIF: intercellular IgG and C3 deposition in a "fish-net" or "chicken-wire" pattern in superficial epidermis.
  • Endemic form in South America is Fogo Selvagem; associated with black fly bites (Simulium).

Practice Questions: Pemphigus Foliaceus

Test your understanding with these related questions

A 70-year-old man comes to the emergency department because of a skin rash and severe itching. He appears ill; there is a generalized skin rash that is scaly, erythematous, and thickened. His palms, soles, and scalp are also involved. Which of the following is the most likely diagnosis?

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Flashcards: Pemphigus Foliaceus

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Direct immunofluoresence showing granular deposits at the tips of dermal papillae points to the diagnosis of _____

TAP TO REVEAL ANSWER

Direct immunofluoresence showing granular deposits at the tips of dermal papillae points to the diagnosis of _____

dermatitis herpetiformis

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