## Histopathology of Pemphigus Vulgaris **Key Point:** The hallmark histological finding in pemphigus vulgaris is **intraepidermal acantholysis** with **suprabasal blister formation**. This distinguishes it from other bullous disorders. ### Microscopic Features 1. **Acantholysis**: Loss of intercellular adhesion between keratinocytes due to disruption of desmosomes by anti-Dsg3 antibodies. 2. **Suprabasal Blister**: The blister cavity forms just above the basal layer, leaving a single row of basal cells attached to the basement membrane ("tombstone" appearance). 3. **Intact Basal Layer**: The basal keratinocytes remain attached to the basement membrane via hemidesmosomes. 4. **Minimal Inflammation**: Unlike pemphigoid, inflammatory infiltrate is typically sparse. ### Comparison with Other Bullous Disorders | Disorder | Location | Histology | Immunology | |---|---|---|---| | Pemphigus Vulgaris | Intraepidermal (suprabasal) | Acantholysis, tombstone cells | IgG anti-Dsg3 ± Dsg1 (intercellular) | | Pemphigus Foliaceus | Intraepidermal (subcorneal) | Acantholysis at granular layer | IgG anti-Dsg1 (intercellular) | | Bullous Pemphigoid | Subepidermal | Subbasal blister, eosinophil-rich | IgG anti-BP180/BP230 (linear at BMZ) | | Dermatitis Herpetiformis | Subepidermal | Microabscesses at dermal-epidermal junction | Granular IgA at dermal-epidermal junction | **High-Yield:** - **"Tombstone" cells** = basal keratinocytes standing alone after acantholysis (pathognomonic for pemphigus vulgaris) - **Intercellular IgG** on direct immunofluorescence ("tombstone" pattern) **Clinical Pearl:** The level of acantholysis (suprabasal vs. subcorneal) correlates with clinical phenotype: suprabasal = mucosal involvement; subcorneal = superficial cutaneous disease (pemphigus foliaceus). **Mnemonic:** **SUPRABASAL = VULGARIS** (mucosal disease, deeper split); **SUBCORNEAL = FOLIACEUS** (cutaneous disease, superficial split). 
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