Viral Infections USMLE Step 1 Practice Question

A 28-year-old woman with HIV presents to the clinic with a 3-week history of progressive cognitive decline, memory loss, and difficulty concentrating. She denies headache, fever, neck stiffness, or focal neurological deficits. Her CD4+ count is 45 cells/μL. Vital signs are stable (BP 118/76, HR 88, RR 16, T 37.2°C). Lumbar puncture reveals CSF with protein 85 mg/dL (normal: 15-45), glucose 55 mg/dL (serum glucose 95 mg/dL), and negative bacterial culture. Brain MRI shows multiple ill-defined white matter lesions in the subcortical and periventricular regions without mass effect, enhancement, or edema. Which of the following is the most likely diagnosis?