If the mother becomes infected during pregnancy, the fetus is at risk regardless of whether or not the mother is symptomatic. Congenital infection is most severe if acquired in the first or second trimester. Seventy-five percent of infants born with congenital toxoplasmosis infection will be asymptomatic. Eight percent will show severe CNS impairment, which might not manifest for several years. In the immunocompetent host, infection with T gondii may be indistinguishable from infectious mononucleosis.
Ocular toxoplasmosis occurs from activation of cysts deposited in or near the retina.
Focal, necrotizing retinitis is the characteristic lesion. Since most cases of ocular toxoplasmosis are the result of congenital infection, clinical manifestation later in life usually represents reactivation of latent infection. Clinical manifestation may mimic other opportunistic infections. Necrotizing encephalitis, pneumonitis, and myocarditis are the most common autopsy findings. The most frequent clinical findings reflect involvement of these 3 organ systems.