[The neuropathology of the acquired immunodeficiency syndrome (AIDS)].

The nervous system is frequently involved in patients with AIDS. The lesions can be due to the human immunodeficiency virus (HIV), to opportunistic agents, to the development of tumours, and to occasional nonspecific factors, such as circulatory, metabolic and degenerative changes. The changes directly related to the presence of the HIV include the HIV encephalitis and leucoencephalopathy, the diffuse polydystrophy and the vacuolar myelopathy. The pathogenesis of these lesions is not yet completely clear. Macrophages are the main cells infected by the HIV, and it seems that the cytotoxic effects on the nervous tissue are indirect, may be due to the release of substances by infected macrophages. Among the opportunistic infections, the most frequent is toxoplasmosis followed by cryptococcosis and cytomegalovirus infection, with some differences in series from various countries. Many other agents have been observed in the brain of patients with AIDS. B-cell lymphoma is the most frequent tumour found in the brain and it is not uncommon the association of infections and/or tumours.