Epstein-Bass virus infection and primary central nervous system lymphoma.

Epstein-Barr virus (EBV) is a double-stranded DNA virus of 172 kbp. It is classified as a lymphocryptovirus in the gammaherpesvirus group. Infection with EBV is very common, usually occurring early in life, and is endemic in all human populations. There are two main types of EBV infection, lytic and latent. The infection occurs even in populations that are geographically isolated, thus indicating that EBV is a fairly ancient virus. Encephalitis is an uncommon manifestation of acute EBV infection but is well described. The diagnosis of EBV-related disease must be planned thoughtfully, choosing appropriate methods to answer well-defined questions. Primary central nervous system (CNS) lymphomas (PCNSL) is an EBV-associated opportunistic neoplasm of the brain found in patients with very advanced HIV disease, having very low CD4+ T-cell counts. This is the most common CNS manifestation of EBV infection in AIDS patients, although with the advent of highly effective combination antiretroviral therapy, the disease has become quite uncommon. Infection with EBV is common and lifelong in humans and rarely results in severe disease. Treatment of opportunistic neoplasms is difficult, and the prognosis is still not very good despite the progress that has been made in understanding these tumors. On the other hand, recent basic research has suggested a number of new approaches, and much clinical trial work remains to be done.