The goals of this natural history protocol are to establish a cohort of pediatric and adult patients with vasculitis to prospectively evaluate the signs and symptoms, imaging findings, and blood and tissue biomarkers associated with pathogenesis and disease outcomes. In the small vessel vasculitides, where considerable progress has been made towards identifying pathologic mechanisms of disease, we will focus on elucidating the pathogenic role of neutrophils, selected biomarkers such as SERPINA1, and novel candidate biomarkers in circulating blood and at local tissue sites including the nasal mucosa. In the medium and large vessel vasculitides, we will identify novel candidate biomarkers for disease pathogenesis and outcomes and develop disease activity indices that incorporate existing and novel clinical, laboratory, genomic, and imaging biomarkers. For all types of vasculitis, a goal of the protocol is to identify patients for possible entry into future