A 30-year-old female with a known history of HIV infection presents with severe headaches and focal neurological signs. An MRI shows a single ring-enhancing lesion. What are the potential causes and the next steps?
In an HIV-positive patient, a single ring-enhancing lesion raises suspicion for a brain abscess or a primary central nervous system lymphoma (PCNSL). To differentiate between these two conditions, further investigations such as a lumbar puncture and/or a biopsy might be needed. PCNSL typically occurs in individuals with CD4 counts below 50 cells/mm^3.