Macrophage activation syndrome triggered by methotrexate-related lymphoproliferative disease in a patient with rheumatoid arthritis.

A 56-year-old woman was treated for rheumatoid arthritis for 17 years with methotrexate (MTX). Night sweats, fever and weight loss made her visit our hospital. Although levofloxacin failed to resolve her fever, she was suspected of having sepsis because of pancytopenia, elevated procalcitonin and a nodular lesion in the lung. After urgent hospitalization, she was diagnosed finally with the methotrexate-related lymphoproliferative disorder (MTX-LPD) associated with macrophage activation syndrome (MAS). Her general condition was improved with MTX withdrawal and 5-day high-dose glucocorticoid administration. Thus, even when the patient was critically ill with MAS, no cytotoxic agents were required to control MTX-LPD.