Which histopathological feature best distinguishes pemphigus vulgaris from bullous pemphigoid?

Explanation

## Histopathological Distinction Between Pemphigus Vulgaris and Bullous Pemphigoid ### Key Histological Features **Key Point:** Acantholysis (loss of cell-to-cell adhesion) leading to intraepidermal blister formation is the hallmark and best discriminator of pemphigus vulgaris. This distinguishes it from bullous pemphigoid, which shows subepidermal blistering. ### Comparative Table | Feature | Pemphigus Vulgaris | Bullous Pemphigoid | |---------|-------------------|-------------------| | **Blister location** | Intraepidermal (suprabasal) | Subepidermal | | **Pathology** | Acantholysis | Basal cell detachment | | **Basal layer** | Intact (tombstone appearance) | Destroyed | | **Immunofluorescence** | Intercellular IgG ("chicken wire") | Linear IgG/C3 at BMZ | | **Autoantigen** | Desmoglein 3 (mucosal) / Dsg 1+3 (mucocutaneous) | BP180 and BP230 (hemidesmosomal proteins) | ### Mechanism of Acantholysis in PV 1. IgG antibodies bind to desmoglein 3 (and sometimes desmoglein 1) 2. Disruption of desmosomal adhesion 3. Loss of cell-to-cell contact → acantholysis 4. Blister forms within the epidermis (suprabasal layer) 5. Basal cells remain attached to basement membrane ("tombstone" cells) **High-Yield:** The **suprabasal acantholysis** with preserved basal layer attachment is pathognomonic for pemphigus vulgaris and is the single best histological discriminator. **Clinical Pearl:** On direct immunofluorescence, pemphigus vulgaris shows **intercellular IgG deposition** (between keratinocytes in a "chicken wire" or "tombstone" pattern), whereas bullous pemphigoid shows **linear IgG/C3 at the basement membrane zone**. ### Why Acantholysis is the Best Answer Acantholysis is: - Unique to pemphigus (not seen in bullous pemphigoid) - Visible on routine H&E histology - Directly reflects the pathogenic mechanism (anti-desmoglein antibodies) - Present in all cases of pemphigus vulgaris