Studies of the Natural History, Pathogenesis, and Outcome of Idiopathic Systemic Vasculitis

* INCLUSION CRITERIA SUBJECTS WITH VASCULITIS: Subjects with known or suspected diagnosis of idiopathic systemic vasculitis will be evaluated either at the outpatient or inpatient unit of the Clinical Center as indicated. * Subjects who fulfill modified versions of the 1990 American College of Rheumatology (ACR) Classification Criteria for GPA and PAN * Subjects who fulfill the 1990 ACR Classification Criteria for EGPA, GCA, and TAK * Subjects who fulfill the 2012 Chapel Hill Nomenclature definition for MPA * Subjects with other suspected systemic or single-organ vasculitides EXCLUSION CRITERIA FOR SUBJECTS WITH VASCULITIS: * Subjects \< 3 years of age * Active malignancy, infection, or any medical condition that in the opinion of the investigator would warrant exclusion * Inability to provide consent, or in the case of minors, assent * Subjects with bleeding diathesis or on anticoagulant medications (e.g. coumadin, heparin, clopidogrel but not including aspirin or NSAIDs) are excluded from participation in nasal brushing or biopsy studies Reason for early termination -Withdrawal of consent INCLUSION CRITERIA FOR HEALTHY VOLUNTEERS: Healthy volunteers will be recruited to serve as controls for studies on peripheral blood samples. -Volunteers able to provide consent, or in the case of minors, assent EXCLUSION CRITERIA FOR HEALTHY VOLUNTEERS: * Volunteers \< 3 years of age risk * Diagnosis of vasculitis or other autoimmune/autoinflammatory disease, including systemic lupus erythematosus, rheumatoid arthritis, sarcoidosis, mixed connective tissue disease or any overlap autoimmune syndrome * Active malignancy, infection, or any medical condition that in the opinion of the investigator would warrant exclusion * Pregnant (by history of last menstrual period) or breast-feeding subjects * Subjects with bleeding diathesis or taking anticoagulant medications (e.g. coumadin, heparin, clopidogrel but not including aspirin or NSAIDs) are excluded from participating in nasal brushing studies