Toxoplasma
encephalitis (TE) is usually diagnosed in advanced stages of
HIV infection when the CD4+ count is <100-200 cells/µl. A 55-year-old woman with HIV/
AIDS, well controlled on antiretroviral
therapy (ART), CD4+ count in the 300 cells/μl range for >1 year presented with acute onset of
headache,
nausea and
vomiting. She had been on her current ART regimen consisting of
raltegravir, co-formulated
emtricitabine/
tenofovir and
etravirine for three years and had been off Pneumocystis prophylaxis for 10 months (
trimethoprim-sulfamethoxazole). Brain MRI showed multiple ring-enhancing, supratentorial and infra-tentorial parenchymal lesions suspicious for
metastases. She had no other evidence of metastatic disease in her body. The possibilities of TE and primary CNS
lymphoma were considered but deemed unlikely given the high CD4+ count. A brain biopsy demonstrated Toxoplasma tachyzoites. There was no evidence of
lymphoma or
carcinoma. Anti-toxoplasma treatment yielded good initial clinical and radiographic responses. While on TE maintenance
therapy, she developed similar symptoms. Repeat MRI showed progression of lesions. Further work-up including CSF Epstein-Barr virus PCR and SPECT Th 201 imaging was not conclusive for CNS
lymphoma. The patient's clinical condition deteriorated and she died. We postulate that functional immunological dysfunction is a possible mechanism by which our patient developed TE despite demonstrating sustained immune response on ART.