Cerebral toxoplasmosis

Case contributed by Ernest Lekgabe
Diagnosis certain


Presented with confusion. Background history of acute myeloid leukemia (AML) treated with bone marrow transplantation.

Patient Data

Age: 65 years
Gender: Male

MRI brain


Ring enhancing lesion in the right cerebral peduncle with a thick but smooth rim. The rim is relatively T2 hypointense. Surrounding vasogenic edema and mass effect. Central restricted diffusion.


MICROSCOPIC DESCRIPTION: The sections show scattered chronic inflammatory cells in the parenchyma and in a perivascular distribution. They are mainly lymphocytes with some histiocytes. No neutrophils or eosinophils. There is one toxoplasma cyst containing bradyzoites (H&E stain). No tachyzoites. No granulomas or viral inclusions. The lymphoid cells show reactive changes. No evidence of malignancy.

Gram, Grocott and Ziehl-Neelsen stains (not shown) did not show the presence of bacteria, fungi or acid fast bacilli, respectively. 

CMV and HSV1-2 immunostains (not shown) were negative. Most of the lymphocytes are CD3+ T-cells. No evidence of lymphoma/leukemia.

Diagnosis: Cerebral toxoplasmosis.

Case Discussion

Toxoplasmosis is an opportunistic infection in patients who are immunocompromised, either due to induced immunosuppression after organ transplantation, like in this case or due to HIV/AIDS. It is caused by the parasite Toxoplasma gondii, and usually as reactivation of latent infection. A significant proportion of the population has a latent infection (seropositive for the parasite). Cats are the definitive hosts for the parasite. Primary CNS lymphoma is an important differential diagnosis, especially if the lesion is solitary.

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