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progressive multifocal leukoencephalopathy (PML)


  • a rare, but often fatal demyelinating disease of the central nervous system caused by reactivation of human polyomavirus (the JC virus - named after the patient it was initially cultivated from - John Cunningham)
  • death can occur weeks to months after onset
  • ~50% of the world's population are infected by the virus by age 20yrs, although most remain asymptomatic
  • PML results from reactivation of this virus due to immunosupression such as in:
    • lymphoproliferative disorders
    • immunosupression following solid organ transplants
    • immunosupressant medications such as:
      • cyclophosphamide
      • mycophenolate mofetil
      • monoclonal antibodies (eg. rituximab, natalizumab)

clinical features

  • progressive neurologic features over the course of a few weeks
  • early signs may be cognitive dysfunction such as mental slowness, disorientation, and behavioural changes
  • motor, gait, visual and sensory disturbances may occur
  • less common features include seizures and headache


  • consider PML in any person with progressive neurologic sugns or symptoms who is immunosupressed and has MRI evidence of multiple characteristic lesions
  • JC virus DNA on quantitative PCR of cerebrospinal fluid (CSF) - but may be false negative early


  • generally supportive
  • restore immune capacity if possible eg. cease immunosuppressants
  • no antiviral agents currently available (2013)
  • recovery of the immune system can trigger immune reconstitution inflammatory syndrome (IRIS) which may require RX with corticosteroids
pml.txt · Last modified: 2013/03/17 17:15 (external edit)