PML and rheumatic disease 4.33/5 (3)

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PML when treated with rituximab. Chakraborty S, Open. CC BY NC ND 3.0


JC (John Cunningham) virus (JC virus, JCV) is a polyoma virus (related to BK virus). It causes Progressive multifocal leukoencephalopathyi (PML) (see below) which is one demyelinating disease (may resemble MS) in people with a weak immune system, for example during anti-rheumatic treatment with rituximab (MabThera, Rixarthon). Primary infection is likely to occur via respiratory tract and mouth. The virus is latent (not active) to 30-70% of healthy individuals.


  • PML incidence (prevalence) is 1: 200.000 but almost only in immunosuppressed individuals
    • Low number lymphocytes (especially T cells) (a subset of white blood cells) over time is risk factor

Disease Cause

  • Reactivation of JC polyoma virus, most often when the immune system is impaired
  • Viruses travel to the brain where the disease develops


  • Cognitive problems (concentration, memory, learning ability, communication)
  • Coordination difficulties (balance, perform coordinated movements)
  • Paresis (paralysis), field of vision loss
  • It is not common with fever or other typical signs of infection


  • New neurological symptoms should suspect PML
  • MRI of the brain
    • Many scattered small or large changes in white matter that usually do not take up contrast agent (unlike inflammatory areas)
    • The lesions can sit anywhere (large brain, small brain, brain stem, but most often subcortical. The changes may resemble those seen MS
  • PCR examination from CSF can detect JC virus. The amount of viruses can be low. It is recommended to examine at least 1ml fluid
  • Brain biopsy ensures the diagnosis
    • Histopathology (tissue sample, biopsy): Enlarged oligo-dendroglial cell nuclei at the boundary of demyelination and JC virus can be detected
  • Blood tests
    • Test (antibody) on virus is possible by JVC-ELISA technique, but the tests are (as of 2017) not fully developed for routine use (Stratify JCV, Biogen)
    • Examination of immune status with counting of CD4 and CD8 positive T lymphocytes is recommended.

Differential diagnoses (similar conditions)


  • Stop immunosuppressive treatment
  • Medications are considered to be removed from circulation by plasmapheresis
  • Immune Reconstitution Inflammatory Syndrome (IRIS) As a complication treated with corticosteroids
  • Of antiviral agents (interferon, ciclofovir, cytarabine), it is only cytarabine that works, but comes poorly to the CNS (brain and spinal cord).
  • Mefloquine is an antimalaria drug that may have effect

Medical prognosis

Severe disease, 20XNXX% dies during the first few months. Many of those who survive get permanent damage (reference: Adang L, 2015)


Opportunistic infections,

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