Lichen Planus

Lichen planus (LP) is an inflammatory condition with a prevalence of around 1% in the USA, affecting skin, mucosa, hair, and nails, and is equally distributed among genders. It is self-limited, potentially resolving within 1 month to 7 years, and is associated with hepatitis C, with the strength of this association varying by the background hepatitis C rates. LP is characterized by polygonal, violaceous papules and plaques, and can lead to scarring alopecia, particularly in the form of lichen planopilaris (LPP), which is more common in women. LP also increases the risk of cutaneous malignancy, especially in oral and genital forms. Diagnosis is made via biopsy and direct immunofluorescence testing. Treatment options include topical and systemic corticosteroids, oral retinoids, and phototherapy, with a lack of strong evidence-based recommendations due to insufficient randomized controlled trials. Other treatments used in case reports include ciclosporin, mycophenolate mofetil, and thalidomide, while nail LP remains difficult to treat and prone to relapse.