Primary central nervous system malignant lymphoma in a patient with rheumatoid arthritis receiving low-dose methotrexate treatment.

We report the first case of primary central nervous system lymphoma (PCNSL) developing in a patient with rheumatoid arthritis (RA) undergoing low-dose methotrexate therapy (LD-MTX). The characteristic clinical management and course in our experience of the present case illustrate the important points about PCNSL in methotrexate-associated lymphoproliferative disorders (MTX-LPD). The number of cases of MTX-LPD in RA patients may increase in the future, since current treatment strategies for RA recommend starting MTX use in early stage RA, and recent insights have tended to show an increase with higher doses.