Lichen sclerosus et atrophicus is a skin disease of multifactorial etiology which appears in patients with genetic or hormonal predisposition and autoimmune disease. Genetic predisposition is suggested by familial reports of the disease which involve twins, siblings, and mother-daughter/son series. This is a report of the occurrence of lichen sclerosus et atrophicus in monozygotic twin women, suggesting that inheritance is of relevance in the etiology of this disease.