What is lichen planus?

➢ Pruritic, Purple, Polygonal, Planar Papules, and Plaques” are the tongue-twisting Ps that describe this disorder of skin and squamous mucosa. ➢ The lesions may result from a CD8+ T cell–mediated cytotoxic response against antigens in the basal cell layer and the dermoepidermal junction that are produced by unknown mechanisms, perhaps as a consequence of a viral infection or drug exposure