Review Note

{{c1::Progressive multifocal leukoencephalopathy (PML)::Condition}}: Demyelinating disease caused by a papova virus. Occurs only in immunosuppressed patients, especially in AIDS. caused by reactivation of JC virus. Progressive course to death within months. In non-AIDS patients, has a predilection for occipital lobes. In AIDS patients, any part of brain may be involved. High T2 and low T1 lesions within subcortical and deep white matter. Mass effect and contrast enhancement are almost always absent.