To estimate the prevalences of polyarteritis nodosa (PAN), microscopic polyangiitis (MPA), Wegener's granulomatosis (WG), and Churg‐Strauss syndrome (CSS).

Cases were collected in Seine–St. Denis County, a northeastern suburb of Paris, which has 1,093,515 adults (≥15 years), 28% of whom are of non‐European ancestry. The study period encompassed the entire calendar year 2000. Cases were identified by general practitioners, the departments of all the public hospitals and 2 large private clinics, and the National Health Insurance System. The Chapel Hill nomenclature was used to define MPA, and American College of Rheumatology criteria to define WG and CSS; PAN was diagnosed based on clinical laboratory, histological and/or angiographic findings. Three‐source capture–recapture analysis was performed to correct for incomplete case ascertainment.

A total of 75 cases were retained and capture–recapture analysis estimated that 23.8 cases had been missed by any 1 of the 3 sources. Accordingly, prevalences per 1,000,000 adults (95% confidence interval [95% CI]) were estimated to be 30.7 (95% CI 21–40) for PAN, 25.1 (95% CI 16–34) for MPA, 23.7 (95% CI 16–31) for WG, and 10.7 (95% CI 5–17) for CSS. The overall prevalence was 2.0 times higher for subjects of European ancestry than for non‐Europeans (P = 0.01).

This study provides the first prevalence estimates for these 4 vasculitides for a multiethnic, urban population. The significantly higher prevalence observed for Europeans may infer a genetic susceptibility of Caucasians. Compared with previous estimates based mostly on rural populations, the higher frequency of PAN and the lower frequency of WG might suggest specific environmental etiologic factors.