Case 126. Toxoplasma encephalitis in AIDS (55 y-o M)
    Multifocal necrotizing brain lesions accompanying visual dysfunction and convulsion    
Key words : Toxoplasma gondii, necrotizing encephalitis, AIDS
opportunistic infection, zoonosis
A large irregular-shaped necrotic lesion is seen at the base of left frontal lobe (gross findings). Similar lesions were also seen in the right hemisphere and cerebellum.   At the periphery of the necrotic lesion, pseudocysts (terminal colonies) containing numerous basophilic granules are observed (HE). No cellular reaction is seen.
The tachyzoites within the pseudocysts are stained black with Grocott's silver. PAS reactivity is also noted.   In another area, the basophilic crescent-shaped tachyzoites are dispersed within the edematous neuropil (HE).
Antiserum to Toxoplasma gondii clearly demonstrates tachyzoites dispersed within the involved brain tissue (immunostaining).   Reference case 126A
Another case (44 y-o M) of Toxoplasma encephalitis in AIDS. In this necrotic brain lesion, only a few Toxoplasma cysts are noted (HE). Careful observation under suspicion of toxoplasmosis is requested for proper histologic diagnosis.
Reference case 126A
Another case (44 y-o M) of Toxoplasma encephalitis in AIDS. Antiserum to Toxoplasma gondii is reactive with the cysts located at the periphery of the brain lesion (immunostaining).
  Toxoplasma cysts under latent infection in mouse brain
Two mature cysts containing bradyzoites are observed in the cerebral cortex (HE). Under the immunosuppressed state, transformation of the bradyzoites of the cyst into tachyzoites may occur in the brain.