Vasculitis is a rare disease in which inflammation in arteries results in reduced blood-flow to important organs such as the kidneys, lungs and brain. Fortunately, advances in treatment have been life-saving for many children and adults; however, research shows that in many adults the disease comes back and there is a high chance of developing permanent damage to organs over time. Researchers have found some “markers” in adults with vasculitis that help predict which patients will end up having more severe disease. Due to the rarity of vasculitis in children, we do not know if the chance of the disease returning, the risk of damage, and the “markers” of severe disease are the same as in adults. This study will allow us to find answers to these questions and help doctors to better counsel patients about prognosis and best treatments.