A 52-year-old woman presents with painful erosions on the buccal mucosa and gingiva for 3 months. Examination reveals reticular white lines (Wickham's striae) on the oral mucosa. Which is the most common site of involvement in lichen planus?

Explanation

## Most Common Site of Oral Lichen Planus **Key Point:** The buccal mucosa and attached gingiva are the most frequently involved sites in oral lichen planus, accounting for approximately 60–70% of oral cases. ### Site-Specific Frequency in Oral LP | Site | Frequency | Clinical Presentation | |------|-----------|----------------------| | Buccal mucosa & gingiva | 60–70% | Reticular pattern, erosions, erythema | | Dorsal tongue | 20–30% | Reticular or atrophic pattern | | Hard palate | 10–15% | Reticular or erosive form | | Ventral tongue | 5–10% | Erosive, painful lesions | | Lip vermillion | Rare | Atrophic, erosive | **High-Yield:** The **buccal mucosa** is the single most common site; when combined with attached gingiva, this represents the majority of oral lichen planus presentations. The reticular (Wickham's striae) pattern is pathognomonic and most visible on the buccal mucosa. ### Clinical Pearl Oral lichen planus often presents as a **reticular (lacy) pattern** on the buccal mucosa, which is asymptomatic. Erosive variants (particularly on the ventral surface and gingiva) are painful and may require systemic corticosteroids. The presence of Wickham's striae on the buccal mucosa is a diagnostic hallmark. ### Why Buccal Mucosa? The buccal mucosa is the most common site because: 1. It is a high-friction area exposed to trauma and irritants 2. It has a thin, non-keratinized epithelium susceptible to T-cell infiltration 3. It is the primary site of reticular pattern formation in lichen planus [cite:Robbins 10e Ch 25]