In pemphigus vulgaris, the histopathological hallmark is acantholysis. At which level of the epidermis does acantholysis characteristically occur?

Explanation

## Histopathology of Pemphigus Vulgaris **Key Point:** Pemphigus vulgaris causes **suprabasal acantholysis** — loss of cell-to-cell adhesion in the layer immediately above the basal keratinocytes. ### Acantholysis Patterns in Pemphigus Subtypes | Pemphigus Type | Acantholysis Level | Causative Antibody | |---|---|---| | **Pemphigus Vulgaris** | **Suprabasal** | Anti-Dsg3 ± Anti-Dsg1 | | Pemphigus Foliaceus | Subcorneal | Anti-Dsg1 only | | Paraneoplastic Pemphigus | Suprabasal + superficial | Anti-Dsg3, anti-Dsg1, anti-envoplakin | ### Microscopic Features 1. **Acantholysis** — loss of desmosomes between keratinocytes 2. **Basal cells remain attached** — "tombstone" appearance (basal layer intact, cells above are separated) 3. **Intraepidermal bulla** — fluid-filled cavity within epidermis 4. **Minimal inflammation** — unlike bullous pemphigoid **High-Yield:** The **basal layer is preserved** in PV — this is the key distinguishing feature from subepidermal blistering disorders. The acantholysis occurs *above* the basal layer, leaving basal cells anchored to the basement membrane. **Clinical Pearl:** The "tombstone" keratinocytes are basal cells standing alone after suprabasal acantholysis. This appearance is pathognomonic for pemphigus vulgaris on H&E staining. **Mnemonic:** **SB-PV** — **S**uprabasal acantholysis in **P**emphigus **V**ulgaris.