A 35-year-old woman presents with reticulate lacy white patches on bilateral buccal mucosa and erosive red patches on the tongue. She has purplish flat-topped papules on bilateral wrists. Which investigation best confirms the diagnosis and differentiates this from oral leukoplakia?
- A Biopsy showing band-like lymphocytic infiltrate at DEJ with saw-tooth rete ridges ✓
- B Tzanck smear from the buccal lesion
- C Periodic acid-Schiff staining for Candida hyphae
- D Direct immunofluorescence showing IgG at basal layer
Correct answer: A. Biopsy showing band-like lymphocytic infiltrate at DEJ with saw-tooth rete ridges
Explanation
Oral lichen planus presents classically with Wickham's striae (lacy white reticular pattern) on buccal mucosa, combined with cutaneous lesions (flat-topped violaceous papules with Wickham's striae on skin). Biopsy confirming lichenoid pattern — band-like lymphocytic infiltrate at the DEJ, vacuolar degeneration of basal layer, saw-tooth rete ridges, and colloid bodies — differentiates OLP from leukoplakia (which shows dysplastic changes). DIF in LP shows fibrinogen at BMZ (shaggy pattern), not IgG. Tzanck smear is for viral/acantholytic disorders.
Reference: Neena Khanna Illustrated Synopsis of Dermatology & STD, 6th ed.
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