A 40 year old Caucasian patient presents with difficulty in speaking and walking for 3 days, in a background of fever and fatigue for 1 week. He has been HIV-positive for 7 years. Close questioning reveals poor compliance with HAART. There is no contact history with tuberculosis nor a travel history to South America. He keeps a cat as a pet. He is allergic to sulfa-drugs. A CD4 count is performed and is found to be 100 cells/microL.
CSF analysis: protein 70 mg/dL (18 - 58 mg/dL) . All other indices within normal parameters Negative for Acid Fast Bacilli and cryptococcal antigens. PCR for HSV-1 and HSV- 2 : negative PCR for M. tuberculosis : negative PCR for T. gondii: positive
The gadolinium enhanced MRI scan shows multiple, small, ring enhancing lesions involving the right frontal lobe, right thalamus and right superior cerebellar peduncle, with surrounding edema. The lesion in the right frontal lobe demonstrates the 'eccentric target sign'. A mass effect is not evident.
Toxoplasma IgG: positive
You suddenly wonder if a brain biopsy is really indicated.