Lichen Planus By Shinjita Das, MD, Harvard Medical School Reviewed / Revised Aug 2021 | Modified Sep 2022 View Patient Education Etiology Symptoms and Signs Diagnosis Prognosis Treatment Key Points Topic Resources Lichen Planus (Forearm) Lichen Planus Lichen Planus (Outer Thigh) Lichen Planus (Arm) Lichen Planus (Hand) Lichen Planus (Oral) Lichen Planus of the Nail Lichen planus is a recurrent, pruritic, inflammatory eruption characterized by small, discrete, polygonal, flat-topped, violaceous papules that may coalesce into rough scaly plaques, often accompanied by oral and / or genital lesions.