Published: 3 March 2016


Reminder: Immunomodulatory Medicines and Risk of Progressive Multifocal Leukoencephalopathy

Prescriber Update 37(1): 10
March 2016

Key Messages

  • Immunomodulatory medicines are associated with the development of progressive multifocal leukoencephalopathy (PML).
  • PML is a demyelinating disease of the CNS caused by the JC virus.
  • A diagnosis of PML should be considered in patients taking immunomodulatory medicines who present with progressive neurological symptoms.

Progressive multifocal leukoencephalopathy (PML) is a demyelinating disease of the central nervous system. PML is caused by the human polyomavirus John Cunningham (JC) virus and may be fatal or result in severe disability.

A compromised immune system due to either disease or immunomodulatory medicines is the major risk factor for development of PML1. Cases of PML have been reported in individuals with HIV, lymphoproliferative disorders and malignancies1.

Medicines associated with an increased risk of PML, either alone or with other immunomodulatory medicines, include:

  • fingolimod
  • azathioprine
  • natalizumab
  • rituximab
  • dimethyl fumarate
  • alemtuzumab
  • mycophenolate mofetil
  • cyclophosphamide
  • tacrolimus.

PML should be considered in patients with compromised immune systems that present with progressive neurological signs or symptoms including cognitive dysfunction, and motor and sensory disturbance1.

More detailed information on PML can be found in the 2012 Prescriber Update article PML: A rare but serious disease’1.

  1. Medsafe. 2012. PML: A Rare but Serious Disease. Prescriber Update 33(3): 21-23. URL: (accessed 3 November 2015).
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