Snapshot A 47-year-old man is brought to the emergency room by his wife for right leg weakness. He first had some right lower leg weakness a week ago which progressed to almost full paralysis of the entire right leg. He has a past medical history of HIV infection, though he has not been on any antiretroviral medications and does not follow up at his HIV clinic regularly. His last CD4 cell count was 2 years ago and was > 500/μL. On physical exam, he is unable to move his right leg. A brain MRI shows non-enhancing white matter lesions. A lumbar puncture is done and the cerebral spinal fluid is sent for polymerase chain reaction testing. He is started on antiretroviral medications. Introduction Classification login to view 5 more bullets Epidemiology login to view 15 more bullets Pathogenesis login to view 4 more bullets Prognosis login to view 1 more bullet Presentation Symptoms login to view 3 more bullets Physical exam login to view 7 more bullets Imaging Brain magnetic resonance imaging (MRI) login to view 4 more bullets Studies Labs login to view 3 more bullets Brain biopsy login to view 6 more bullets Making the diagnosis login to view 1 more bullet Differential Cerebral toxoplasmosis login to view 2 more bullets Treatment Management approach login to view 2 more bullets Conservative login to view 3 more bullets Medical login to view 3 more bullets Complications Permanent neurologic sequelae PML-immune reconstitution inflammatory syndrome login to view 5 more bullets