Dermatology

Lichen planus

Lichen planus is an inflammatory interface dermatosis causing pruritic violaceous papules with Wickham striae and potentially persistent disease of the mouth, genitals, scalp or nails.

Definition

Lichen planus is a chronic inflammatory lichenoid disorder of the skin, mucous membranes, hair and nails, characterised by an immune-mediated interface dermatitis and a variable risk of scarring or mucosal complications.

First principles

Recognise the lichenoid pattern

Cutaneous lichen planus classically produces flat-topped, shiny, pink-purple or darker papules and plaques with fine white Wickham striae, often on the flexor wrists, ankles and lower back. Koebnerisation can occur at sites of trauma, and healing may leave post-inflammatory hyperpigmentation, particularly in skin of colour.

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