Progressive Multifocal Leukoencephalopathy Progressive multifocal leukoencephalopathy (PML) is a life-threatening disorder of the nervous system that typically affects individuals with suppressed immune systems. The disorder, which is caused by the so-called ‘JC virus,’ is characterized by demyelination or destruction of the myelin sheath that covers nerve cells. Unfortunately, there have been reports of people suffering from PML while taking a psoriasis drug called Raptiva. Progressivemultifocalleukoencephalopathy.net~Site InfoWhoisTrace RouteRBL Check