Epidemiology of the vasculitides.

In summary, systemic vasculitides constitute a heterogeneous group of overlapping diseases that are somewhat more common than previously considered. Although the causes of vasculitis are largely unknown, epidemiologic studies have implicated geographic, genetic, and environmental factors. Ethnicity, various genes such as those of the MHC, gender, and environmental factors seem to account for the different incidence rates of these syndromes. GCA is the most common vasculitis in elderly people from Western countries. Small-sized cutaneous vasculitides, particularly HSP in children and HV in adults, are also common diseases. Increased physician awareness and the routine use of ANCA tests may contribute to an increase in the recognition of conditions such as WG and MPA.