Background:Lichen planus is an uncommon disorder of unknown cause that most commonly affects middle-aged adults. Lichen planus may affect the skin (cutaneous lichen planus), oral cavity (oral lichen planus), genitalia (penile or vulvar lichen planus), scalp (lichen planopilaris), nails, or esophagus.The frequency of LP varies on the basis of the population studied, with a particularly high rate of disease noted on the Indian subcontinent. LP most commonly affects middle-aged people, although childhood-onset LP has also been well described. Women are affected as frequently as men. LP is a self-limited condition that, according to one epidemiologic study, may resolve after 1 month to 7 years. A range of topical and systemic medications have been shown to improve the symptoms associated with LP and to hasten the resolution of LP.The pathogenesis of LP is not entirely understood. In general, activated T lymphocytes are recruited to the dermal–epidermal junction and induce apoptosis in basal keratinocytes. Both CD4+ and CD8+ T lymphocytes are found in the lichenoid infiltrate of LP, with a predominance of the latter cell type being present in established lesions.