Progressive Multifocal Leukoencephalopathy - Cause

Cause

The cause of PML is a type of polyomavirus called the JC virus (JCV), after the initials of the patient from whose tissue the virus was first successfully cultured. Recent publications indicate 39% to 58% of the general population are seropositive for antibodies to JCV, indicating current or previous infection with virus. The virus can cause persistent asymptomatic infection in approximately one-third of the adult population, based on viral shedding into the urine from the site of asymptomatic infection in the kidney. The virus causes disease only when the immune system has been severely weakened.

Prior to the advent of effective antiretroviral therapy, as many as 5% of people with AIDS eventually developed PML. It is unclear why PML occurs more frequently in AIDS than in other immunosuppressive conditions; some research suggests the effects of HIV on brain tissue, or on JCV itself, make JCV more likely to become active in the brain and increase its damaging inflammatory effects.