Epstein-Barr virus-positive multiple myeloma developing after immunosuppressant therapy for rheumatoid arthritis: a case report and review of literature.

A 61-year-old woman was diagnosed as having rheumatoid arthritis (RA) and began treatment with salazosulfapyridine (SASP) and methotrexate (MTX) in 2008; the administration of concomitant tacrolimus (TAC) was initiated in 2010. She subsequently developed concurrent multiple myeloma (MM), immunoglobulin G (IgG)-κ type, in 2012. A portion of the tumor cells tested positive for Epstein-Barr virus-encoded small RNA (EBER). MTX treatment was discontinued in 2014, and the exacerbation of MM ensued. The patient received two cycles of bortezomib plus dexamethasone (BD) therapy and attained a complete response (CR). She then underwent an autologous peripheral blood stem cell transplantation. The Epstein-Barr (EB) virus infection arising from the increased RA disease activity and immunosuppressant medication might have influenced the development of MM in this case. Most reported patients with EB virus-positive plasmacytoma are in a state of immunosuppression, and this condition may fall within the category of other iatrogenic immunodeficiency-associated lymphoproliferative disorders. No other reports of plasmacytoma occurring in a background of RA or after TAC or MTX therapy have been made, and the present case is the first such report.