HIV-related demyelinating disease

True demyelination, or at least a leukoencephalopathy with predominant involvement of myelin, may occur in many neurological complications of human immunodeficiency virus (HIV)-infection, resulting from various mechanisms which are not all well understood. These include lesions directly related to infection of the nervous tissue by HIV, opportunistic infections and lymphomas secondary to the cell-mediated immunodeficiency, and changes due to other general or systemic complications of acquired immunodeficiency syndrome (AIDS). HIV-induced pathology of the nervous system includes HIV-specific disease, due to direct infection of the nervous system by the virus. This is characterized by the presence of distinctive multinucleated giant cells and white matter changes, HIV encephalitis and HIV leukoencephalopathy, which may overlap in one third of cases. The pathogenesis of myelin destruction is unclear. Direct infection of neurons or glial cells has never been demonstrated. Indirect immunopathologic, toxic, metabolic, or vascular mechanisms secondary to infection of monocytes/macrophages are more likely. Less specific HIV-associated central nervous system (CNS) pathology including vacuolar myelopathy, and vacuolar leukoencephalopathy are characterized by numerous vacuolar myelin swellings in spinal or cerebral white matter. The exact aetiopathological relationship of these changes to HIV infection is uncertain. It seems likely that factors other than, or additional to, HIV infection play a role in their causation. Apart from these changes which usually occur at the late stages of the disease, acute perivenous inflammatory leukoencephalopathy, presenting either as acute haemorrhagic leukoencephalopathy, acute demyelinating perivenous encephalitis, or acute multiple sclerosis-like leukoencephalopathy revealing HIV-infection occur in rare cases.(ABSTRACT TRUNCATED AT 250 WORDS)