Progressive multifocal leukoencephalopathy (PML) is a demyelinating disease which results from the JC virus infecting oligodendrocytes. It is considered the most common clinical manifestation of JC virus infection in the brain.

The main differential diagnosis of this image pattern within the clinical context is the HIV encephalopathy. PML usually presents asymmetric lesions, predominantly in the parietal lobes, which start in the juxtacortical white matter and cross to the contralateral hemisphere through the corpus callosum.