In patients with human immunodeficiency virus (HIV) infection, toxoplasmic encephalitis (TE) is a common cause of space-occupying brain lesions, but primary central nervous system lymphoma (PCNSL) can likewise present as a focal brain lesion and has a poor prognosis. Therefore, distinguishing TE from PCNSL is important, but usually difficult. We herein on report a rare case for TE complicated with PCNSL in a patient with HIV infection. He was referred to our hospital with tonic-clonic seizures. He had been treated for TE and HIV infection for 5 years, but he stopped going to the hospital 2 years previously. His CD4-positive cell count was 2/μL and the serum anti-Toxoplasma IgG antibody was positive. Cranial magnetic resonance imaging (MRI) showed a 2.7-cm nodule with the eccentric target sign and surrounding edema in the right parietal lobe. Thallium-201 scintigraphy showed an uptake in the nodule. Both Epstein-Barr virus and Toxoplasma gondii DNAs were detected in the cerebrospinal fluid with the polymerase chain reaction (PCR) technique. Because empiric treatment for TE failed to improve his symptoms, a brain biopsy was performed and showed PCNSL on histopathologic examination and Toxoplasma DNA on PCR. After whole-brain radiation therapy, dexamethasone, and antiretroviral therapy, his symptoms and MRI abnormalities improved. A brain biopsy and Toxoplasma PCR test should be considered in cases with atypical clinical presentation.
