What are the key imaging features and clinical associations of Progressive Multifocal Leukoencephalopathy (PML) in immunocompromised patients?

PML is a demyelinating disease caused by the JC virus, a member of the Polyomaviridae family, primarily affecting immunosuppressed individuals, such as those with AIDS. Key MRI findings include multifocal, asymmetric white matter lesions without mass effect or enhancement. Clinical pearls include rapid progression of neurological deficits and the absence of significant inflammatory response. Common mimickers include multiple sclerosis and HIV encephalopathy, but PML typically lacks the mass effect seen in these conditions.