Lichen sclerosus is a chronic inflammatory disease of unknown origin, which affects mostly women in the fifth and sixth decades of life, but can also occur in men and children. The involvement of the oral mucosa alone or together with other forms of presentation is extremely rare, requiring a differential diagnosis with other diseases of the oral cavity, particularly lichen planus. There are less than 30 cases of lichen sclerosus in the oral mucosa described in the literature and there are no reports on malignant transformation so far. We describe a patient with skin, oral and genital lesions of lichen sclerosus.