LAUSR

Abstract Objectives To determine the clinical characteristics of methotrexate-associated lymphoproliferative disorder (MTX-LPD). Methods In this study, 12 RA patients who developed MTX-LPD were assessed. The peripheral blood lymphocyte (PBL) count at the onset of MTX-LPD was compared to that 6 months before the onset, in Epstein-Barr virus-encoded RNA (EBER)-positive and -negative subgroups. We examined the change in the PBL count after MTX withdrawal. In patients with relapsed LPD, changes in the PBL count before relapse were also examined. Results Regression of LPD after MTX withdrawal was noted in eight patients. In these patients, the PBL count was decreased at the onset of MTX-LPD compared to 6 months before the onset; the decrease was significantly more prominent in EBER-positive patients. In cases of spontaneous regression of LPD, the PBL count recovered quickly after MTX withdrawal. Four of eight patients showed a recurrence of LPD after they improved following MTX withdrawal. These patients also exhibited a decreased PBL count at recurrence compared to 6 months before recurrence. Conclusion A decrease in the PBL count might be involved in the pathogenesis of MTX-LPD, especially in EBER-positive cases and in patients with LPD relapse after MTX withdrawal following initial improvement.