Clinicopathological study of severe chronic active Epstein-Barr virus infection that developed in association with lymphoproliferative disorder and/or hemophagocytic syndrome.

Chronic active Epstein-Barr virus (CAEBV) infection has been previously reported to be sometimes associated with an aggressive clinical course. However, the role of EBV in the CAEBV is not well clarified. A retrospective study was performed on nine adult and five child patients (eight males and six females). Histologically, at first admission, the presence of neoplastic lesions could not be confirmed. The lymph nodes in half of all cases revealed paracortical hyperplasia with transformed lymphocytes (hyperplastic type). Half of the cases showed non-suppurative necrosis and an increased number of histiocytes with phagocytosis (histiocytic type). Activated histiocytes with lymphokine positivity were frequently detected in the histiocytic type. In the phenotypical study, 10 of the examined 11 cases showed increased numbers of natural killer (NK) cells and/or CD8-positive T lymphocytes. In situ hybridization (ISH) showed EBV-infected lymphoid cells, but the number of EBV-infected cells varied. Double-labeling immunochemistry/ISH demonstrated EBV-infected T cells, including NK cells, but not B cells. In addition, three cases showed a monoclonal dissemination of EBV terminal repetitive sequence (TR), and two cases showed oligoclonal dissemination. From those findings, monoclonal, oligoclonal and polyclonal populations of EBV-infected T or NK cells were considered to be present in CAEBV states. During the clinical course, 12 of the 14 cases died within 5 years. Six cases died from EBV-associated hematopoietic tumors (histiocytic tumor, T cell lymphoma, B cell lymphoma, plasmacytoma, and NK cell leukemia); one from non-EBV-associated acute myelogenous leukemia, and five due to hemophagocytic syndrome. The examined EBV-associated hematopoietic tumors showed monoclonal EBV terminal repetitive sequences. There is a possibility that the monoclonal dissemination of EBV-infected cells develops from oligoclonal or polyclonal EBV-infected cells. And active histiocytes with lymphokine positivity were frequently detected in the cases with histologically histiocytic type. These findings seem to be related with the causes of death due to hemophagocytic syndrome.