Granulomatosis with polyangiitis (GPA), previously known as Wegener's granulomatosis (WG), is an extremely rare long-term systemic disorder that involves the formation of granulomas and inflammation of blood vessels (vasculitis). It is a form of vasculitis that affects small- and medium-size vessels in many organs but most commonly affects the upper respiratory tract, lungs and kidneys. [Source: Wikipedia 
]
