Progressive Multifocal Leukoencephalopathy

PML is a demyelinating disease of the CNS caused by reactivation of the polyomavirus JC (JC virus). It is found almost exclusively in immunosuppressed patients (only case reports of immunocompetent people). It is most commonly thought of in the HIV population (especially with CD4 <200) however should also be considered in other immunocompromised patients such as those with myeloproliferative / lymphoproliferative disorders.

This disease is a progressive multifocal disease involving the white matter of the CNS. It typically presents with subacute neurologic deficits including altered mental status, motor deficits, ataxia and / or visual symptoms. About 20% will eventually have seizures.

Although a brain biopsy is gold standard, diagnosis of PML is generally made on clinical grounds with supportive imaging and presence of JC virus in CSF. CT scan may show multiple hypodense patchy or confluent regions. MRI shows decreased T1 lesions or increase signal on T2 weighted images. An LP sent for JC virus – PCR is helpful. Without HAART the sensitivity of CSF PCR was 70-90% however in patients on treatment the yield is lower. Although brain biopsy is gold standard for diagnosis it is generally deferred due to high morbidity.

The prognosis of PML is poor with median survival (IN HAART TREATED PTS) approximately 1.8 years. Median survival is much less in non-treated HIV patients and <3 months in people with PML who are not HIV infected (myeloproliferative disorders etc.)