A 45-year-old HIV-positive man with CD4 count below 100 cells/mmL develops progressive cognitive decline and visual field defects. MRI shows multifocal asymmetric white matter lesions in the parieto-occipital regions involving subcortical U-fibers, with no mass effect, no enhancement and sparing of the cortex. What is the most likely diagnosis?

• A Primary CNS lymphoma
• B HIV encephalopathy
• C Progressive multifocal leukoencephalopathy ✓
• D Acute disseminated encephalomyelitis

Explanation

Progressive multifocal leukoencephalopathy, caused by reactivation of JC virus in severely immunosuppressed patients, produces multifocal demyelinating white matter lesions that characteristically involve the subcortical U-fibers, spare the cortex, and show neither enhancement nor mass effect because the blood-brain barrier remains intact. Primary CNS lymphoma enhances avidly and shows mass effect. HIV encephalopathy causes symmetric periventricular disease with diffuse atrophy rather than discrete U-fiber lesions.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.