Methotrexate-associated lymphoproliferative disorder with histopathological features of histiocytic necrotizing lymphadenitis.

An 84-year-old Japanese woman suffering from rheumatoid arthritis (RA), who had been treated with methotrexate (MTX) for 15 years, was admitted to our hospital for generalised lymphadenopathy, thrombocytopenia, anaemia, elevated aminotransferases, and elevated CRP levels. Pathological findings of cervical lymph node biopsy were compatible with histiocytic necrotising lymphadenitis (HNL). Small lymphocytes positive for Epstein-Barr virus (EBV)-encoded small RNA were detected in the tissue. We suspected a MTX-associated lymphoproliferative disorder (MTX-LPD), withdrew MTX and administered leucovorin (folic acid). The patient's symptoms gradually resolved following discontinuation of MTX. We considered that this patient developed HNL as an MTX-LPD when EBV was reactivated. This is the first case of HNL associated with MTX treatment for RA, which we report here along with clinical course.