Progressive Multifocal Leukoencephalopathy

PML is a severe and often fatal (30-50% mortality) reactivation of latent viruses in immunocompromised hosts caused by the JC virus.

Cause: Human polyoma virus (Papovavirus family)
Transmission: respiratory/oral
Symptoms: asymptomatic infection in immunocompetent host; multiple dispersed lesions in white matter of brain leading to impairment of mental function, paralysis and death
Pathogenesis: JCV infects respiratory/GI epithelia --> viremia --> kidneys --> CNS --> demyelination
Complications: high mortality (up to 90%) in < 2 years
Treatment: none (other than reversal of immunocompromising condition)
Vaccine: none