ACTIVE HUMAN HERPESVIRUS (HHV-6) INFECTION OF THE CENTRAL-NERVOUS-SYSTEM IN PATIENTS WITH AIDS

White matter disease is a relatively common neuropathological change o bserved in the central nervous system (CNS) tissues of patients with A IDS at autopsy. This disease ranges from small foci of myelin loss to extensive areas of demyelination. In the studies reported here, four o f six unselected adult patients with AIDS had areas of demyelination i n their CNS tissues at the time of their deaths. In the tissues examin ed, the severity of the demyelinative disease varied among the patient s from a single focus of demyelination to essentially confluent loss o f myelin in subcortical white matter and other CNS structures, The dem yelinative disease in the brains of these patients was closely associa ted with active HHV-6 infection. The infected cells were present only in areas of demyelination, and they were never observed in tissue area s free of pathological changes. The HHV-6-associated neuropathology ob served in the brains of these patients was identical to that described in an adult bone marrow transplant (BMT) patient with fatal HHV-6 enc ephalitis. Thus HHV-6-induced white matter disease appears to be a dis tinct pathological syndrome, Pathogenic mechanisms involved in this di sease are unknown. However, the existence of HHV-6 leukoencephalopathy in a BMT patient demonstrates the potential for HHV-6 to cause this s yndrome without need for a cofactor or copathogen such as HIV.