Lichen sclerosus (LS) is a chronic dermatosis that primarily involves the anogenital area. It is characterized by an initial inflammatory phase that is often followed by changes to genital architecture and skin atrophy if left untreated. It is more common in females, with 2 reported peaks of onset, the first in premenarchal girls and the second in postmenopausal women, but it is thought that onset during the reproductive years is likely underrecognized. Childhood and adolescent cases in boys have increasingly been recognized.

The pathogenesis of LS is unknown, but an autoimmune mechanism with genetic predisposition is hypothesized, with an increased prevalence of HLA-DQ7, DQ8, DQ9, and DR12. Some studies implicate Borrelia spp and Epstein-Barr virus (EBV) infection, and trauma and hormonal influences have been investigated. LS has also been reported in the setting of immune checkpoint inhibitor therapy.

Over 85% of lesions are found on anogenital skin. In this location, LS usually presents as dry, tender, and severely pruritic atrophic white plaques. In females, characteristic sites include the clitoris and clitoral hood, interlabial sulci, labia minora, and perineum. Plaques can progress to cause agglutination of labia minora to adjacent mucosa, and phimosis of the clitoral hood to the clitoris. Sclerosis of the vaginal introitus, with resultant dyspareunia, can also occur. Secondary erosion or ulceration may lead to burning and pain, especially after micturition.

The majority of cases of male genital LS occur in uncircumcised men. The glans and prepuce are most frequently affected. Meatal involvement may occur. Scarring complications include urinary obstruction, ulceration, painful erection, and phimosis. There may also be diminished sensation of the glans and sexual dysfunction.

Squamous cell carcinoma can arise in untreated genital lesions.

LS may also occur on extragenital skin and rarely on the oral mucosa. The Koebner phenomenon, with development of LS at sites of trauma, has been reported. Extragenital LS is frequently asymptomatic; however, it can be pruritic.