Granulomatosis with polyangiitis (GPA), formerly known as Wegener's granulomatosis, is a form of vasculitis, an abnormal inflammation of the blood vessels. Its cause is not known, and it most frequently affects the respiratory tract (sinuses, nose and lungs) and the kidneys. Other organs that can be affected are the skin, nerves, joints, eyes and ears. It can develop at any age but it most commonly appears in people between the ages of 40 and 65.