A 47-year-old man with a history of recent subclinical hepatitis C infection presents complaining of rash and mouth pain for the past week. The rash is pruritic. Examination reveals lesions on his wrists, ankles, and scalp; the lesions are shiny, violaceous, sharply demarcated, confluent papules containing fine white lines in a lacy pattern on their surfaces. Examination of his oropharynx reveals an erosion on the left buccal mucosa with the same fine white reticulation. Which of the following is the most likely diagnosis?

Classic description of lichen planus "5 P's": Purple, Polygonal, Pruritic, and Planar Papules and Wickham's striae (the characteristic light grey or white lines or dots seen on the surface of lichen planus). It affects middle-aged adults and may be associated with hepatitis C infection and/or drug exposure The rash of Erythema multiforme typically involves the extremities, palms, and soles, and may consist of erythematous or purpuric plaques and bullae with central clearing. Painful lesions are typical, though pruritus can be present as well. Mucous membrane involvement is common. Hypersensitivity vasculitis is typically drug-induced but may also result from hepatitis B or C infection. It manifests as palpable purpura and skin biopsy shows a leukocytoclastic vasculitis. Viral exanthema rashes of widely varying morphology, common in children, typically more erythematous and macular, as opposed to the violaceous and papular lesions described here.