Abstract
Methotrexate （MTX）-associated lymphoproliferative disorder is one of the side effects of MTX, and their reports in the oral cavity are rare. We report a case in which an ulcer in the mandibular gingiva gradually caused a bone exposure. The diagnosis was suggested by biopsy. The lesion disappeared after the withdrawal of MTX. In the treatment of the ulcerative lesions without bone exposure in a patient receiving MTX, this side effect should be taken into consideration, and the general diagnosis should involve a histopathological examination at an early stage.
