Case of the Week
Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
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April 28, 2014
Toxoplasmosis
- Toxoplasmosis is the most common space-occupying lesion in AIDS patients.
- Headache is the most common presenting symptom. Other symptoms may include fever, seizure, focal deficits, and confusion.
- Key Diagnostic Features:
- Ring-enhancing lesion(s)—often multiple, but solitary in 30%, and often involving thalami/basal ganglia
- Eccentric target sign described, which is 95% specific and 30% sensitive
- Markedly elevated lipid/lactate on MR spectroscopy
- DDx:
- Lymphoma (higher choline than toxoplasmosis, less dramatic lipid/lactate peak on MRS, target sign less common)
- Brain abscess (central restricted diffusion, no target sign)
- Metastasis (known primary present, no restricted diffusion, less common lipid/lactate peak)
- Rx: Empiric 7–10 day course of sulfadiazine+pyrimethamin. Spiramycin is used in pregnancy before 18 weeks. Lifelong prophylaxis is recommended in HIV patients. If poor response, biopsy is recommended to rule out other possibilities.
