A 52-year-old woman presents with flaccid blisters and erosions on her oral mucosa and inner cheeks for 3 weeks. Histopathology shows acantholysis with tombstone appearance. Which is the most common site of initial presentation in pemphigus vulgaris?

Explanation

## Most Common Site of Initial Presentation in Pemphigus Vulgaris **Key Point:** The oral mucosa is the most common site of initial presentation in pemphigus vulgaris, occurring in 50–90% of patients at onset. ### Clinical Significance **High-Yield:** Oral involvement typically precedes cutaneous manifestations by weeks to months. This makes early recognition of oral erosions critical for diagnosis. ### Why Oral Mucosa? 1. **Thin epithelium** — The oral mucosa has a thinner stratum corneum and reduced keratinization compared to skin, making it more susceptible to acantholysis. 2. **Constant mechanical trauma** — Chewing, swallowing, and friction from teeth and food accelerate blister formation and erosion. 3. **Moisture environment** — The wet oral environment promotes rapid breakdown of blisters into painful erosions. ### Progression Pattern | Site | Frequency at Onset | Typical Timeline | |------|-------------------|------------------| | Oral mucosa | 50–90% | Initial (weeks 1–4) | | Buccal mucosa | Most common intraoral | Early | | Palate | Common | Early | | Cutaneous (face, chest, axillae) | 50–70% | Later (weeks 4–12) | | Palms and soles | Rare | Late/severe disease | **Clinical Pearl:** A patient with painful oral erosions that do not respond to topical antifungals or antivirals, combined with flaccid blisters elsewhere, should raise suspicion for pemphigus vulgaris. Oral involvement without cutaneous disease at presentation is common and should not delay diagnosis. ### Diagnostic Approach **Mnemonic:** **ORAL-PV** (Oral mucosa is the Recognizable Appearance in Lesions of Pemphigus Vulgaris) 1. **Clinical history** — Ask about mouth ulcers preceding skin lesions. 2. **Intraoral examination** — Look for erosions on buccal mucosa, hard palate, gingiva. 3. **Histopathology** — Acantholysis with suprabasal cleft (tombstone keratinocytes). 4. **Immunofluorescence** — Direct immunofluorescence (DIF) shows intercellular IgG and C3 ("tombstone" pattern). [cite:Robbins 10e Ch 25]