Vasculitis
Abstract 2126: Incidence and Pevalence of Wegener’s Granulomatosis, Microscopic Polyangiitis, and the Churg-Strauss syndrome in southern Sweden
Authors: Aladdin Mohammad, Lennart T H Jacobsson, Gunnar Sturfelt, Marten Segelmark
Background: Estimates of the epidemiology of primary systemic vasculitis are primarily limited to a handful of areas with static or well-characterized populations. This study estimates the annual incidence rates and point prevalences of polyarteritis nodosa and the ANCA-associated vasculitides in Southern Sweden.
Study Design: Incidence and point-prevalence rates were calculated for the Lund-Orup-Landskrona Health Care District, which is in the southernmost county in Sweden, and has an adult population (defined as 15 years or older) of 233, 433 inhabitants. Patients were identified based on pathology and laboratory records obtained from local institutions (including the University of Lund), and a medical registry that includes national identification numbers. Each case was reviewed to confirm the diagnosis of vasculitis; overlap was eliminated by using national identification numbers, which are assigned to all citizens and permanent residents. Cases were classified using the Chapel Hill Consensus Conference definitions and the American College of Rheumatology 1990 classification criteria.
Results: Forty-six new cases of vasculitis were diagnosed between 1 January 1997 and 31 December 2002; 23 patients had Wegener’s granulomatosis, 18 patients had microscopic polyangiitis, 3 patients had polyarteritis nodosa, and 2 patients had the Churg-Strauss syndrome. This yielded an annual incidence of 16.4 per million for Wegener’s granulomatosis, 12.8 per million for microscopic polyangiitis, 2.1 per million for polyarteritis nodosa, and 1.4 per million for the Churg Strauss Syndrome. The point prevalence per million as of January 1, 2003 was 197 for Wegener’s granulomatosis, 116 for microscopic polyangiitis, 39 for polyarteritis nodosa, and 17 for the Churg Strauss syndrome. The overall point prevalence was 368 cases per million, and 74.4% of cases occurred in patients older than 55 years.
Editorial Comments: This study adds significantly to our understanding of the epidemiology of systemic vasculitis in a previously-unreported region of the world, particularly because it demonstrates an unexpectedly high prevalence of systemic vasculitis. There has been a theory that the prevalence of vasculitis is increasing worldwide, possibly due to the presence of environmental toxins. This study ostensibly supports this thesis, although the unusually high prevalence noted is probably at least in part due to the careful manner in which patients were captured, and the existence of the Swedish national health system, which facilitates identification of patients. It is also interesting to note the low prevalence of polyarteritis nodosa in this group, which is likely the result of the Chapel Hill Consensus Conference, which reclassified the majority of these patients as having microscopic polyangiitis.