Diffuse large B-cell lymphoma of the central nervous system in mycophenolate mofetil-treated patients with systemic lupus erythematosus

Patients with systemic lupus erythematosus (SLE) are susceptible to the development of lymphoproliferative disorders and postulated causes include intrinsic defects in immune surveillance and iatrogenic administration of immunosuppressants. Since the introduction of mycophenolate mofetil (MMF) to the immunosuppressive regimen for the management of post-organ transplantation, there have been reports of primary lymphoma of the central nervous system (PCNSL). MMF has been widely used to treat active SLE patients with Class IV lupus nephritis. In addition to two previously reported cases of PCNSL among SLE patients on long-term MMF, we report a third patient who has been on treatment with MMF for 8 years. The histology showed features compatible with diffuse large B-cell lymphoma with strong immunohistochemical staining for CD20 and positive signal for Epstein-Barr virus (EBV)-encoded RNA by in-situ hybridization that is similar to other case reports, suggesting EBV driven B-cell lymphoproliferative disease. The patient responded to withdrawal of MMF, intravenous methotrexate, rituximab and whole brain radiotherapy. With the increasing use of MMF in active renal as well as non-renal exacerbations of SLE, PCNSL should be included in the differential diagnosis in patients who present with gradual onset of focal neurological deficit.