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The contrasting epidemiology of granulomatosis with polyangiitis (Wegener's) and microscopic polyangiitis

Richard A Watts1, Janice Mooney, Jane Skinner

  • 1Norwich School of Medicine, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK. richard.watts@ipswichhospital.nhs.uk

Rheumatology (Oxford, England)
|January 20, 2012
PubMed
Abstract

Insights

The incidence of granulomatosis with polyangiitis (GPA) shows a cyclical pattern, suggesting infection may influence its occurrence. Microscopic polyangiitis (MPA) incidence did not show a clear cyclical pattern, indicating potentially distinct causes for GPA and MPA.

Area of Science:

  • Rheumatology
  • Epidemiology
  • Immunology

Background:

  • Granulomatosis with polyangiitis (Wegener's) (GPA) and microscopic polyangiitis (MPA) are rare systemic vasculitides with unknown etiologies.
  • Investigating epidemiological patterns may offer insights into distinct causative factors for GPA and MPA.

Purpose of the Study:

  • To investigate the epidemiology of GPA and MPA in a defined population.
  • To identify differences in the occurrence patterns of GPA and MPA that might suggest distinct etiologies.

Main Methods:

  • A prospective register of systemic vasculitis patients at Norfolk and Norwich University Hospital was maintained from 1988 to 2010.
  • Incident cases of new-onset GPA and MPA were identified using the European Medicines Agency algorithm within a specific geographic area.
  • Population data for 2008 was used to estimate incidence rates.

Main Results:

  • 111 GPA and 58 MPA incident cases were identified between 1988 and 2010.
  • The overall annual incidence was 11.3/million for GPA and 5.9/million for MPA.
  • GPA incidence exhibited a cyclical pattern with a 7.6-year periodicity, peaking in 2005, while MPA incidence showed no convincing periodicity.

Conclusions:

  • The distinct epidemiological patterns, particularly the cyclical incidence of GPA, support the hypothesis that GPA and MPA are separate conditions with different etiologies.
  • The cyclical nature of GPA incidence may indicate an influence of infection on its occurrence.

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