Development of Intravascular Large B-cell Lymphoma during Methotrexate Treatment for Rheumatoid Arthritis

A 56-year-old woman with rheumatoid arthritis who had been taking methotrexate (MTX) for six years visited our hospital with dyspnea and dizziness. Abdominal ultrasonography revealed mild splenomegaly. Laboratory examinations showed a marked elevation in soluble interleukin-2 receptor and lactate dehydrogenase levels. These abnormalities revealed a spontaneous regression after MTX discontinuation, however, they worsened again four months later. Skin biopsies revealed a diagnosis of intravascular large B-cell lymphoma (IVLBCL), and we diagnosed MTX-associated IVLBCL (MTX-IVLBCL) based on its characteristic course. Despite the recurrence of IVLBCL, it showed a good response to chemotherapy. MTX-IVLBCL should therefore be treated with consideration since it has different characteristics from that of de novo IVLBCL.