Seasonal variations in onset of Wegener's granulomatosis: Increased in summer?

Objective. Investigators have reported significant seasonal variations of onset of Wegener's granulomatosis (WG), but those data were not confirmed by others. We reexamined the hypothesis of a seasonal pattern of onset of WG. Methods. We conducted telephone interviews with 59 patients with newly diagnosed WG fulfilling the American College of Rheumatology criteria. Patients were identified having been enrolled from 2001 to 2004 by French hospitals in 2 multicenter therapeutic trials. The interviews investigated precisely how and when their disease had appeared to establish an index date, defined as the year and month of the first symptom(s) attributable to WG. Once telephone interviews had been completed, index dates were also retrieved from medical records. Results. Among the 59 patients interviewed, 14 (24%) were unable to specify an exact month of WG onset. Based on the remaining 45 "informative" patients, the month of onset distribution varied significantly (p = 0.03, exact goodness-of-fit chi-square test), notably with a higher onset rate in August (p = 0.001). Seasonal distributions also differed significantly (p = 0.01), with an increased rate of summer onset (June-August) (p = 0.001). Index dates extracted from medical files showed that onset was also more frequent in summer (p = 0.01). Conclusion. Our results confirm the seasonality in onset of WG, but unlike previous reports indicating an increase in winter, instead suggest that this vasculitis preferentially appears in summer. These findings might support an allergic mechanism in the pathogenesis of WG.