The changing pattern of human immunodeficiency virus-associated cerebral toxoplasmosis: a study of 46 postmortem cases.

Frequency, pathogenesis and morphological features of toxoplasmosis were assessed in a consecutive autopsy study. Among 204 patients who died from AIDS in Zurich during 1981-1990, 46 (23%) showed morphological evidence of cerebral toxoplasmosis. In 38 out of 46 cases (83%), toxoplasmosis was restricted to the central nervous system (CNS) and, therefore, pathogenetically classified as reactivation of a latent infection. Acute, systemic toxoplasmosis most frequently involved heart and lungs in addition to the CNS and was observed in 7 cases (15%). These patients probably acquired the infection during HIV-induced immunosuppression. Latent infection with intracerebral tissue cysts but no inflammatory response was present in only one case. Diffuse, necrotizing toxoplasma encephalitis with widespread, confluent areas of necrosis was mainly observed during the early period of the AIDS epidemic and restricted to 6 patients (13%) who did not receive chemotherapy. The majority of patients (83%) had multiple, macroscopically well-circumscribed abscesses with preferential location in the cerebral hemispheres. Of all CNS regions, the rostral basal ganglia were most frequently affected (78% of cases). Since 1989, chronic, burnt-out lesions were observed. These were mainly composed of lipid-laden macrophages and immunocytochemistry for Toxoplasma gondii usually failed to detect the parasite. This changing pattern of CNS lesions probably reflects improved clinical management of patients with AIDS.