A 48-year-old man with a 3-month history of oral erosions and scattered cutaneous blisters on the chest undergoes skin biopsy. Histology shows suprabasal acantholysis with a 'tombstone' appearance of basal cells. Serum testing is positive for anti-desmoglein 3 antibodies. Which feature most reliably distinguishes pemphigus vulgaris from pemphigus foliaceus?

Explanation

## Pemphigus Vulgaris vs. Pemphigus Foliaceus: Key Discriminators ### Histopathological Distinction | Feature | Pemphigus Vulgaris | Pemphigus Foliaceus | |---------|-------------------|--------------------| | **Acantholysis level** | Suprabasal (above basal layer) | Subcorneal (superficial, just below stratum corneum) | | **Basal cell appearance** | 'Tombstone' cells (intact, stand alone) | Acantholytic cells throughout | | **Mucosal involvement** | Common (80–90%) | Rare or absent | | **Cutaneous blisters** | Flaccid, easily ruptured | Flaccid, superficial | ### Serological Distinction **High-Yield:** - **PV:** Anti-desmoglein 3 ± anti-desmoglein 1 - **PF:** Anti-desmoglein 1 **only** (never anti-desmoglein 3) **Key Point:** The presence of **anti-desmoglein 3 antibodies** is **pathognomonic for pemphigus vulgaris** and is absent in pemphigus foliaceus. This serological finding, combined with suprabasal acantholysis and mucosal involvement, definitively distinguishes PV from PF. ### Clinical Correlation **Mnemonic:** **DG3 = Deep (Vulgaris)** - Desmoglein 3 → deeper (suprabasal) split → mucosal involvement → more severe **DG1 = Derm (Foliaceus)** - Desmoglein 1 → dermal-epidermal junction (superficial) → skin only → milder **Clinical Pearl:** Oral mucosa involvement is the clinical hallmark of PV. If a patient with pemphigus has oral erosions, it is PV until proven otherwise. PF spares the mucosa. ### Why Option 0 is Correct The combination of **oral mucosal involvement + suprabasal acantholysis + anti-desmoglein 3 antibodies** is the gold-standard triad that distinguishes PV from PF. Anti-desmoglein 3 is never found in PF.