Progressive multifocal leukoencephalopathy: A rapidly progressive, often fatal viral infection of the brain. Commonly abbreviated as PML.
PML is believed to be due to the Jacob-Creutzfeldt (JC) papovavirus. The virus infects oligodendrocytes (support cells in the brain).
The signs and symptoms of PML include headaches, memory loss, changes in mental status, speech and vision difficulties, loss of strength, limb weakness, seizures, partial paralysis and loss of coordination. The disease leads to coma and then to death.