Childhood chronic vasculitis describes a group of rare life-threatening diseases that have in common inflammation of blood vessels in vital organs such as kidneys, lungs and brain. Most knowledge about them comes from adult patients. Severe disease requires aggressive life-saving treatments with steroids and some cancer drugs which can themselves cause damage, and increase risks of cancer and severe infections. Conversely, milder disease can be treated with less toxic drugs. Different classification and scoring tools are used to define the types and severity of vasculitis and to measure damage caused by disease or drugs. These in turn help direct how aggressively to treat a patient and to measure outcome. None of these tools however have been assessed in children and the best balance of disease and treatment risks against outcome for children is not known. Although causes of these diseases in children and adults are probably the same, the effects of the disease and the response (good and bad) to drugs will differ in growing children. Because specialists may see only one new child with vasculitis each year, obtaining enough information to learn about childhood vasculitis requires cooperation. We will use an international web-based registry to which doctors from 50 or more centers can contribute patient data. We will determine the features which help better classify and diagnose children compared to adults. Through the web we will collect and analyze information on patients similarly classified and scored so that most successful treatments can be identified. Children with vasculitis are less likely to have diseases associated with aging, alcohol and smoking etc., and therefore may be a better group in whom to study the underlying biology of vasculitis. We will use this opportunity and collect spit, blood and tissue from registry patients for laboratory study with an aim to find biomarkers to better classify, define and direct optimal treatment and outcomes.