Progressive multifocal leukoencephalopathy (PML) is a viral infection of oligodendrocytes, astrocytes and glia caused by the John Cunningham virus (JCV) and generally provoked by immunosuppression (HIV, organ transplant, malignancies, rheumatic diseases, medications).

What is Natalizumab/Tysabri?

  • Natalizumab is an immunomodulatory humanized monoclonal antibody used for the treatment of relapsing remitting multiple sclerosis (RRMS)
  • It blocks lymphocytes migration in the central nervous system (CNS) by inhibiting alpha-4 beta-1 integrin.
  • It has been shown to uniquely predispose to PML by certain mechanisms.

Early detection and management of PML

  • Natalizumab-associated PML carries a 20% mortality rate with 40% of survivors having permanent serious disability.
  • No specific treatment is available.
  • Early diagnosis has been associated with better outcome as it allows prompt immune reconstitution through elimination of natalizumab with plasma exchanges or immunoadsorption.

Download the PML information card (PDF) for more information or to bring to your appointment.


UBC MS program medical leads:

  • MS/NMO Program Relapse Nurse: 604-822-0753
  • UBC Hospital Paging Service: 604-822-7121 (ask for the Neurologist on call)
  • MS/NMO Program Fax: 604-297-9685