Fatal Chronic Active Epstein-Barr Virus Infection in a Rheumatoid Arthritis Patient Treated with Abatacept.

Chronic active Epstein-Barr virus (CAEBV) T-cell type infection, systemic form, is characterized by persistent infectious mononucleosis-like symptoms, high EBV DNA levels in the peripheral blood, organ damage, and a poor prognosis. The association between CAEBV and rheumatoid arthritis (RA) is unclear. We report a case of fatal CAEBV T-cell type infection in an RA patient undergoing treatment with cytotoxic T-lymphocyte-associated antigen 4 immunoglobulin fusion protein (abatacept, ABT). CAEBV can rapidly worsen in RA patients receiving ABT. Thus, we should try to establish an early diagnosis in patients with CAEBV infection.