Lichen sclerosus, also known as lichen sclerosus et atrophicus, is a chronic skin thinning disorder of unknown etiology. It is known for creating white, angular, well-defined, papules and plaques. The mean age of onset is 50 years in women and 43 years in men. It can also occur in children but it is much more common in women than men with an incidence ratio of 10:1. It is generally asymptomatic but in the female genital area symptoms such as erosions, painful urination, and painful intercourse may occur. Men may develop recurrent inflammation and pain of the foreskin and even phimosis, a painful stricture of the foreskin around the end of the penis.

In this condition the skin develops a porcelain white, semi-transparent appearance resembling something like mother-of-pearl. On non-genital skin it is generally found on the torso, mainly the upper back, neck, axillae, periumbilical, and the ventral wrists. On the genital skin of women it is usually around the vulva and perineum areas sometimes showing a figure-of-eight distribution in the anogenital area. In men the area of involvement is the glans and undersurface of the foreskin. Although slight there is a risk of developing squamous cell carcinoma in lesions involving the genital skin. Involvement of the general skin can have remissions but not generally in the genital lesions.

Treatment is with topical corticosteroids. In unresponsive cases the use of anti-malarials such has hydroxycholoroquine can be used. In men, circumcision can relieve symptoms of phimosis and may result in remission.