ANCA-Associated Vasculitis (AAV) is a group of autoimmune diseases that cause inflammation of blood vessels, leading to reduced blood flow and potential damage to organs. It is characterized by the presence of antineutrophil cytoplasmic antibodies (ANCA) in the blood, which mistakenly attack the body's own tissues. Common forms of AAV include Granulomatosis with Polyangiitis (GPA) and Microscopic Polyangiitis (MPA). Symptoms can vary widely but often include fatigue, fever, weight loss, and respiratory issues. Early diagnosis and treatment are crucial to manage the condition and prevent serious complications.