A chronic undefined illness characterized by infectious mononucleosis (IM)-like symptoms and signs, possibly
associated with Epstein-Barr virus (EBV) infection, designated as so-called chronic active EBV infection (CAEBV), is
focused and discussed in this mini-review. Patients with CAEBV often develop T cell lymphoproliferative disorder
(LPD)/lymphoma or NK cell LPD/lymphoma. Unique manifestations with generally poor prognosis of the disease prompt
us to understand in particular the entity, diagnosis and treatment.