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Incidence of progressive multifocal leukoencephalopathy in patients with rheumatoid arthritis: a national

Elizabeth V Arkema1, Ronald F van Vollenhoven, Johan Askling

  • 1Clinical Epidemiology Unit (T2), Department of Medicine, Karolinska Institutet, Stockholm SE-171 76, Sweden. earkema@post.harvard.edu

Annals of the Rheumatic Diseases
|June 29, 2012
PubMed
Abstract

Insights

Patients with rheumatoid arthritis (RA) may face a higher risk of progressive multifocal leukoencephalopathy (PML) compared to the general population. This study investigated PML incidence in RA patients, with or without biological agent exposure.

Area of Science:

  • Rheumatology
  • Neurology
  • Epidemiology

Background:

  • Progressive multifocal leukoencephalopathy (PML) is a rare but serious disease.
  • PML cases have been reported in rheumatoid arthritis (RA) patients on biological therapy.
  • Limited data exists on PML incidence in RA patients without biological agent exposure.

Purpose of the Study:

  • To estimate the incidence rate of PML in RA patients.
  • To compare PML incidence in RA patients versus the general population.
  • To assess PML incidence with and without exposure to biological agents.

Main Methods:

  • Utilized Swedish national registries from 1999-2009.
  • Included adult-onset RA patients diagnosed with PML and biological agent exposure.
  • Matched RA patients with general population comparators by age, sex, and county.
  • Calculated crude and standardized incidence rates per 100,000 person-years.

Main Results:

  • The study included 66,278 RA patients and 286,949 general population comparators.
  • PML incidence rate in RA patients was 1.0 (95% CI 0.3 to 2.5) vs. 0.3 (95% CI 0.1 to 0.6) in the general population.
  • Only one PML case was identified among patients exposed to biological agents.

Conclusions:

  • RA patients may have an increased rate of PML compared to the general population.
  • Further research is needed to understand the specific risks and mechanisms involved.

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