We evaluated the postmortem incidence of choroid plexus infection in c
erebral toxoplasmosis in 17 patients with acquired immune deficiency s
yndrome (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%) i
n patients with only the healed cystic lesions of toxoplasmosis. Large
necrotizing abscesses of the choroid plexus were found in three of th
e patients. In one of these, the choroid plexus was the sole site of C
NS infection, which presented as radiographically documented masses in
the third and fourth ventricles associated with obstructive hydroceph
alus. These results demonstrate that infection of the choroid plexus i
s common with cerebral toxoplasmosis and suggest that this infection s
hould be included in the differential diagnosis of intra- or periventr
icular 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 du
e to hematogenous spread to the choroid plexus from reactivation of la
tent organisms from systemic organs rather than to reactivation of lat
ent organisms within the brain itself. Furthermore, the high frequency
of choroid plexitis offers the potential for CSF dissemination of thi
s infection.