Nasal type extranodal NK/T cell lymphoma diagnosed in a patient with rheumatoid arthritis under methotrexate.

: Rheumatoid arthritis (RA) patients have increased risk of lymphoma which seems associated mainly with high inflammatory state and disease activity, but also with immunosuppressive agents or Epstein-Barr virus (EBV) infection. Many case reports describe lymphoproliferative lesions arising during methotrexate therapy, often EBV positive with possible regression after methotrexate withdrawal. The authors report the case of an 85-year-old patient with erosive and seronegative RA, in remission under methotrexate who developed a midfacial destructive lesion with epistaxis and local inflammatory signs. The magnetic resonance imaging showed a large nasal septum defect. Anti-neutrophil cytoplasmic antibodies titres and angiotensin converting enzyme were normal. Biopsies of the lesion identified a NK/ T nasal type lymphoma. EBV latent membrane protein research on the lesion was negative. Polymerase chain reaction analysis of the bone marrow aspirate showed EBV DNA positivity. Withdrawal of methotrexate was performed without tumour regression. The authors described the single case of a patient with RA in stable remission under methotrexate who presented a rare type of lymphoma, a nasal type NK/T. EBV active replication was found in the bone marrow.