For children with vasculitis who are enrolled in the study, clinical information will be obtained from the medical chart from the time of diagnosis, post-induction (3-6 months post diagnosis) visit, 12-month clinic visit, and their most recent clinic visit or last clinic visit before discharge to adult care (ie. final outcome visit). Information that will be collected includes laboratory test results, biopsy and imaging results, disease activity, clinical history, and medications. Blood, urine, and saliva samples will also be collected at each clinic visit. If the subject experiences a disease flare, clinical data and biological samples will be collected at the time of the flare and at a later date when the disease remits.