Fulminant human herpesvirus six encephalitis in a human immunodeficiency virus-infected infant.

Self-limited involvement of the central nervous system (CNS) is a relatively common complication of primary infection with human herpesvirus six (HHV-6) in normal children. We describe an HIV-infected infant who developed fulminant encephalitis as a complication of HHV-6 infection. Immunohistochemical staining of CNS tissue demonstrated productive infection of all CNS cell-types. Analysis of the infected brain tissue by the polymerase chain reaction (PCR) confirmed the presence of a dense HHV-6 infection in the tissue, and demonstrated that the virus present in the CNS tissue was predominantly the A variant of HHV-6. This is the first demonstration of invasive tissue disease caused by HHV-6 in an HIV-infected infant.