1. Presented by Danielle Hutchings, MD and reviewed by Patricia Simner, MSc, PhD

Clinical vignette

A middle-aged patient with recently diagnosed HIV presents with vomiting and severe headache. The patient reports several months of headache and dizziness and describes intermittent fever, fatigue, weight loss and anorexia. They have no other past medical or surgical history and have never been treated for HIV. Initial laboratory workup showed CD4 count of 30 cells/mL and HIV viral load 740,000 copies/mL. CBC was within normal limits and CMP showed hyponatremia. An MRI of the brain with contrast showed two ring enhancing intracranial lesions with edema and mass effect and midline shift.

Question: What is the most likely diagnosis in this patient?