| Disease | Pathophysiology / Target Antigen | Clinical Features & Morphology | Histology / Immunofluorescence (IF) |
|---|---|---|---|
| Pemphigus Vulgaris | IgG against Desmoglein 1 & 3 (Desmosomes) (Type II H.S.) | Flaccid bullae; rupture easily. Oral mucosa involved (often 1st). Nikolsky (+). | Intraepidermal split. ”Row of tombstones” on basalis. IF: Net-like / Reticular IgG pattern. |
| Bullous Pemphigoid | IgG against Hemidesmosomes (BP180/BP230) (Type II H.S.) | Tense bullae; do not rupture easily. Oral mucosa spared. Nikolsky (-). | Subepidermal split. Prominent Eosinophils. IF: Linear IgG at basement membrane. |
| Dermatitis Herpetiformis | IgA against Tissue Transglutaminase (Cross-reacts w/ reticulin) | Pruritic papules/vesicles on extensor surfaces (elbows, knees). Assoc: Celiac Disease. | Microabscesses (neutrophils) at dermal papillae tips. IF: Granular IgA at dermal papillae. |
| Epidermolysis Bullosa | Hereditary defect in anchoring proteins. (e.g., Keratin 5/14 or Collagen VII) | Blisters induced by minor trauma/friction. Presents in infancy/childhood. | Cleavage at Dermal-Epidermal Junction (DEJ). Electron microscopy used for subtypes. |
| Bullous Impetigo | Exfoliative Toxin A (S. aureus) cleaves Desmoglein 1. | Flaccid bullae with honey-colored crust. Rapid spread; contagious. Nikolsky (+). | Subcorneal split (very superficial). Gram stain: Gram (+) cocci in clusters. |