Choroid plexus infection in cerebral toxoplasmosis in AIDS patients.

We evaluated the postmortem incidence of choroid plexus infection in cerebral toxoplasmosis in 17 patients with acquired immune deficiency syndrome (AIDS) and cerebral toxoplasmosis and, by immunohistochemistry, identified Toxoplasma gondii tachyzoites in this structure in 53% of all cases. They were present in 78% of the nine cases with the acute necrotizing stages of CNS toxoplasmosis but were less frequent (20%) in patients with only the healed cystic lesions of toxoplasmosis. Large necrotizing abscesses of the choroid plexus were found in three of the patients. In one of these, the choroid plexus was the sole site of CNS infection, which presented as radiographically documented masses in the third and fourth ventricles associated with obstructive hydrocephalus. These results demonstrate that infection of the choroid plexus is common with cerebral toxoplasmosis and suggest that this infection should be included in the differential diagnosis of intra- or periventricular lesions in patients with AIDS. In addition, the high frequency of choroid plexus infection with acute cerebral toxoplasmosis suggests that cerebral toxoplasmosis in the immunosuppressed patient may be due to hematogenous spread to the choroid plexus from reactivation of latent organisms from systemic organs rather than to reactivation of latent organisms within the brain itself. Furthermore, the high frequency of choroid plexitis offers the potential for CSF dissemination of this infection.