Immunobullous Disorders

Immunobullous Overview - Blister Blueprint

• Definition: Group of autoimmune diseases where autoantibodies target adhesion molecules in skin/mucosa, causing blisters.
• Pathophysiology: Autoantibodies (IgG, IgA) bind to target antigens (e.g., desmogleins, BPAG1, BPAG2), activating complement & inflammatory cells, leading to blister formation.
• Classification (Level of Split):
  • Intraepidermal: Blisters within the epidermis (e.g., Pemphigus group).
  • Subepidermal: Blisters below the epidermis, at dermoepidermal junction (e.g., Pemphigoid group, Dermatitis Herpetiformis).

• Key Diagnostic Tests:
  • Skin Biopsy (H&E): Shows level of split, inflammatory infiltrate.
  • Direct Immunofluorescence (DIF): Detects autoantibodies in perilesional skin (📌 DIF = Deposits in skin).
  • Indirect Immunofluorescence (IIF): Detects circulating autoantibodies in serum (📌 IIF = In serum).
  • ELISA: Identifies specific autoantibodies (e.g., anti-Dsg1, anti-Dsg3, anti-BP180, anti-BP230).

⭐ Nikolsky's sign: Elicited by applying tangential pressure to perilesional skin; positive (epidermis dislodges) in conditions with acantholysis like Pemphigus Vulgaris due to loss of keratinocyte adhesion.

Pemphigus Disorders - Intraepidermal Agony

• Pemphigus Vulgaris (PV):
  • 📌 'Vulgaris is Vicious and Deep': Targets Desmoglein 3 (Dsg3) > Desmoglein 1 (Dsg1).
  • Clinical: Flaccid blisters, common oral erosions, +Nikolsky sign.
  • Histology: Intraepidermal, suprabasal acantholysis, Tzanck cells.
  • DIF: Intercellular IgG/C3 ('chicken-wire' or 'fishnet' pattern).
• Pemphigus Foliaceus (PF):
  • Targets Desmoglein 1 (Dsg1).
  • Clinical: Superficial blisters, crusted/scaly lesions, rare/no oral involvement, +Nikolsky sign.
  • Histology: Superficial acantholysis (granular layer).
• Paraneoplastic Pemphigus: Severe, malignancy-associated (often lymphoproliferative); polymorphic lesions.

Pemphigoid Group - Subepidermal Siege

• Subepidermal autoimmune blistering diseases. Common Direct Immunofluorescence (DIF): linear IgG/C3 deposition at the Basement Membrane Zone (BMZ).

DH, LABD & EBA - Diverse Blister Battles

• Dermatitis Herpetiformis (DH)
  • Intense pruritus; grouped (herpetiform) vesicles on extensors (elbows, knees, buttocks).
  • Strong celiac disease/gluten sensitivity link. Histology: subepidermal, neutrophil microabscesses in dermal papillae. DIF: granular IgA deposits in dermal papillae.
  • 📌 DH = Diet & Dapsone Help. Treatment: Dapsone, gluten-free diet.
  • 

  • ⭐ Dermatitis Herpetiformis is considered a cutaneous manifestation of celiac disease, and a gluten-free diet is a cornerstone of management.

• Linear IgA Bullous Dermatosis (LABD)
  • Heterogeneous presentation. Key: Linear IgA deposition at Basement Membrane Zone (BMZ).
  • Clinical: vesicles/bullae, often annular; classic 'string of pearls' sign.
  • 
• Epidermolysis Bullosa Acquisita (EBA)
  • Autoantibodies against Type VII collagen (anchoring fibrils in BMZ).
  • Presents with trauma-induced blisters, increased skin fragility, scarring, and milia formation. Often resistant to standard treatments.

High‑Yield Points - ⚡ Biggest Takeaways

• Pemphigus Vulgaris: Intraepidermal (acantholysis), Nikolsky +ve, targets Desmoglein 3 (&1).
• Bullous Pemphigoid: Subepidermal, Nikolsky -ve, targets BPAG1/2, tense bullae, eosinophils.
• Dermatitis Herpetiformis: Subepidermal, IgA deposits (papillae), strong celiac disease link.
• Direct Immunofluorescence (DIF): Crucial for diagnosis, shows antibody location/type.
• Linear IgA Bullous Dermatosis: Linear IgA at BMZ; vancomycin common trigger.
• Pemphigus Foliaceus: Superficial, targets Desmoglein 1 only.
• Epidermolysis Bullosa Acquisita: Targets Type VII collagen.