Hypertrophic lichen planus on the ankle of a 39 year old female African American patient. Lichen planus is a common inflammatory disorder of the skin and mucous membranes characterised by purplish, itchy, flat-topped bumps. In the hypertrophic form of the disease the rash develops into scaly plaques. The cause is unknown. Treatment is with topical corticosteroids alongside antihistamines to reduce itching. Most cases of lichen planus disappear within two years.