Malignant Lymphoma in Rheumatoid Arthritis Patients Treated with Methotrexate and Human Monoclonal Antibody

—A Report of 2 Cases—

Abstract

We rarely experience development of malignant lymphoma during rheumatoid arthritis (RA) treatment. We report two cases of malignant lymphoma in patients treated with methotrexate (MTX) and human monoclonal antibody for rheumatoid arthritis. A 55-year-old woman with active RA had been treated with MTX and infliximab therapy. She developed soft tumor in her left arm and skin ulcer on both hands two months after the initiation of infliximab therapy. An open biopsy showed malignant lymphoma. Spontaneous remission of malignant lymphoma was obtained after cessation of infliximab therapy. A 71-year-old woman with active RA had been treated with MTX. She noticed stomatitis in the oral cavity six years after the initiation of MTX therapy. Gingival biopsy in the right maxilla showed malignant lymphoma. After chemotherapy and radiation, complete remission was achieved.
RA patients have an overall two-fold increased risk of malignant lymphoma compared with the general population. RA itself and drugs for RA are considered to be risk factors for the development of malignant lymphoma. We suspect that MTX and human monoclonal antibody are associated with the development of malignant lymphoma in our RA patients.