Background: \- Vasculitis is a group of diseases that inflame and damage blood vessels and tissue. It can cause many medical problems. Few tests can diagnose the disease, and none can reliably predict a relapse. Researchers want to study people s genes and follow people over time to see how the disease affects them.

Objective: \- To learn the signs, symptoms, imaging tests, genetic markers, and blood tests that can help identify people with vasculitis and predict what will happen to them over time.

Eligibility: * People age 3 and older who have or are thought to have vasculitis, or are related to someone with it. * Healthy volunteers.

Design: * Participants will be evaluated by a doctor who has expertise caring for patients with vasculitis. * Participants will give a blood sample. Some will give a urine sample. * Some participants may have brushings or biopsies taken from the inside lining of the nose. * Images of participants blood vessels may be taken using scans. For some scans, participants will lie on a table that moves in and out of a cylinder that takes pictures. For some scans, a contrast agent may be injected into an arm vein. Other scans may use a radioactive form of sugar. Healthy minors will not have scans. * Some participants will answer questionnaires. - Some participants will have their tests done at NIH. Others will have their doctor take the blood, saliva, or cheek swab samples and send them to NIH. * Some participants will have one visit lasting 1-2 (but sometimes up to 4) days. Some participants may have follow-up visits every 3 - 6 months, indefinitely.