Objectives: The epidemiological manifestations of ANCA-associated vasculitis (AAV) differ geographically. However, there have been no prospective studies comparing the incidence of AAV between Japan and Europe over the same time period using the same case definitions.
Methods: The incidence of AAV was determined by a population-based method in Miyazaki prefecture, Japan, and Norfolk, U.K., between 2005 and 2009. Patients with AAV were defined and classified according to the European Medicines Agency (EMEA) algorithm.
Results: The number of incident cases of AAV in Japan and the U.K. were 86 and 50, respectively, and the average annual incidence over the 5-year period was 22.6/million (95% CI 19.1, 26.2) and 21.8/million (95% CI 12.6, 30.9) in Japan and the U.K., respectively. The average age was higher in patients in Japan than in patients in the U.K. [mean (median), 69.7 (72) vs. 60.5 (61) years]. Microscopic polyangiitis (MPA) was the predominant subtype in Japan (83%), while granulomatosis with polyangiitis (Wegener's) was more frequent in the U.K. (66%). As for the pattern of ANCA positivity, >80% of Japanese patients were pANCA/MPO positive, whereas two-thirds of U.K. patients were cANCA/PR3 positive. Renal involvement in MPA was very common in both countries, but was much less common in granulomatosis with polyangiitis in Japan compared with the U.K.
Conclusion: There was no major difference in AAV incidence between Japan and the U.K., but this prospective study found MPA and MPO-ANCA to be more common in Japan and granulomatosis with polyangiitis and PR3-ANCA to be more common in the U.K., in line with earlier reports.