Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is an autoimmune disease where the immune system mistakenly attacks a type of white blood cell called neutrophils. Normally, the immune system works to remove foreign objects by promoting inflammation and releasing destroyer cells. This allows the body to properly remove anything that is not supposed to be in the blood stream. When individuals have ANCA-associated vasculitis, their immune systems attack healthy white blood cells. This causes damage and destruction to the blood vessels. If left untreated this can lead to organ damage, specifically to the kidneys, or death.