Clinical and pathological characterization of oral mucosal 'lichen planus-like lesions' in patients with pemphigus vulgaris: An observational study

Background: Lichen planus-like lesions on oral mucosa occasionally occur in Indian patients with pemphigus vulgaris. Its significance, both clinical and pathological, is yet to be elucidated. Aims and Objectives: To study the clinical and pathological characteristics of clinically apparent oral mucosal lichen planus-like lesions in pemphigus patients and to assess their relation with pemphigus disease activity. Materials and Methods: A total of 32 patients with pemphigus vulgaris who had oral lichen planus-like lesions were included and classified as 'cases,' and eight diagnosed cases of pemphigus vulgaris without lichenoid 'hue' were included as controls. The biopsy specimens were subjected to routine histopathologic examination, immunohistochemistry with FasL, and caspase-3 and direct immunofluorescence. Results: On histopathologic examination, the diagnosis of pemphigus vulgaris, lichen planus, 'overlap' and 'nonspecific' were rendered in 19 (59.4%), 4 (12.5%), 5 (15.6%) and 4 (12.5%) cases, respectively. On immunohistochemistry, FasL was positive in epithelial cells in 16 (50%) cases and 4 ( 12.5%) controls (P = 0.066). Caspase-3 stained positively in 18 (56.2%) cases and 20 (62.5%) controls (P = 0.77). Direct immunofluorescence was positive in 77.8% (21/27) of the cases. Limitations: Relatively small number of controls is the limitation of this study. Conclusion: Lichen planus-like lesions in pemphigus should not be labeled as inactive disease or postinflammatory hyperpigmentation. Apoptosis followed by pigment incontinence seems to explain such lesions with 'lichen planus-like appearance' in oral pemphigus vulgaris. Active pemphigus smoulders in a majority of these lesions.