Epstein-Barr virus-positive T/NK-cell lymphoproliferative diseases in children and adolescents

In primary Epstein-Barr virus (EBV) infection, the virus may infect T-cells or natural killer (NK)-cells and can cause T- and NK-cell (T/NK-cell) lymphoproliferative disease, which encompasses several disease entities with a broad clinicopathological spectrum. T/NK-cell lymphoproliferative disease arising during primary EBV infection includes clonal EBV-infected T-cell proliferation in the setting of infectious mononucleosis, EBV-associated hemophagocytic lymphohistiocytosis, and systemic T-cell lymphoma of childhood. Chronic active EBV (CAEBV) infection of the T/NK-cell type is not a simple viral infection but instead is classified as a lymphoproliferative disease. The prototype of CAEBV is a systemic form that exhibits varying degrees of clinical severity depending on the host immunity and EBV factor. Hydroa vacciniforme-like lymphoproliferative disease and mosquito-bite allergy are peculiar cutaneous forms of CAEBV that involve T/NK-cells, respectively. Abnormal activation and replication of EBV together with the proliferation and clonal expansion of infected cells, depending on the patient's immunological response, play a key role in the pathogenesis of CAEBV of the T/NK-cells type.