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As knowledge of the epidemiology of primary systemic vasculitides (PSV) is fragmentary, we attempted to investigate the incidence of temporal arteritis (TA), Takayasu’s arteritis (TAA), polyarteritis nodosa (PAN), Wegener’s granulomatosis (WG), Churg-Strauss syndrome (CSS), Henoch-Schönlein purpura (HSP), and hypersensitivity vasculitis (HSV) in Vilnius according to the American College of Rheumatology (ACR) 1990 criteria and to compare the data with the results from selected European studies.1
To be included in this study the patients had to (a) have been diagnosed with systemic vasculitides in the 10 year period from 1990 to 1999 and (b) have been resident in Vilnius at the time of diagnosis. Patients referred to Vilnius University Hospital rheumatology department were prospectively included in the study. Also, the patients’ registration books from tertiary nephrology, dermatology, and internal medicine departments were searched for a diagnosis of PSV retrospectively, but following the same inclusion criteria. Additionally, the data files of the centre of pathology available from 1995 onwards, including renal register, were searched.
We applied ACR 1990 criteria for the classification of PSV; however, for patients classified as HSV, the term cutaneous leucocytoclastic vasculitis (LCV) was equally used.2 Patients with microscopic polyangiitis (MPA) were included in the PAN group, and PAN criteria applied to both conditions. The group of PAN and HSV/LCV were reanalysed according the definition for MPA. The denominator population was the adult population over 16 years from Vilnius city, which comprised 468 504 people (53.7% female) in 1999.
Overall, we identified 205 patients according to inclusion criteria—an annual incidence of 43.8/106 (95% confidence interval (CI) 38.1 to 50.3) (table 1). The most common type of vasculitis was HSV/LCV with an annual incidence of 26.0/106 (95% CI 21.7 to 31.2). The incidence of PAN was found to be 7.7/106 (95% CI 5.5 to 10.7), HSP 3.0/106 (95% CI 1.7 to 5.1), TA 2.3/106 (95% CI 1.2 to 4.3), WG 2.1/106 (95% CI 1.1 to 4.1), TAA 1.3/106 (95% CI 0.5 to 2.9), and CSS 1.3/106 (95% CI 0.5 to 2.9) annually. Six patients in the PAN group and eight in the HCV/LCV group responded to the definition of MPA being antineutrophil cytoplasmic antibody (ANCA) positive and/or having nephritis in addition to other system involvement. Therefore, the annual incidence of presumed MPA was 3.0/106 (95% CI 2.0 to 5.7) in total. The diagnoses of 66/205 patients were supported by biopsy data. Five of 36 patients with PAN, 8/10 patients with WG, and 4/5 with CSS were found to be ANCA positive.
Three studies, Kristiansand (Norway),5 Norwich (Norfolk, England)3,4,6, and Lugo (Spain)7 were selected for comparison with our study (table 1). The annual incidence of PSV in Vilnius seems to fall in between the figures of annual incidence reported in Norwich (38.6/106, TA excluded), Kristiansand (54.5/106), and Lugo (115.0/106). However, the distribution of the annual incidence of distinct vasculitides differs from those of other European studies. The most important difference was noted for TA and less notably for WG (table 1). The annual incidence of MPA was in accordance with the lower figures reported in the European studies and less than half that quoted in the study by Watts et al.3
The shorter life expectancy of Lithuanian people, which in 1999 was 71 years and lower than that of the European population, might be a potential explanatory factor for the lower incidence of TA in Vilnius. Possibly, because a histological examination was rarely carried out, and the ANCA test was introduced only after 1995,8 WG and other ANCA associated vasculitides cases are underrepresented, especially in the first 5 years of this study.