Multisystem disease chiefly affecting males, characterized by necrotizing granulomatous vasculitis involving the upper and lower respiratory tracts, glomerulonephritis, and variable degrees of systemic small vessel vasculitis; considered an aberrant hypersensitivity reaction to an unknown antigen.

Granulomatosis with polyangiitis (GPA), formerly known as Wegener's granulomatosis (WG), after German physician Friedrich Wegener, is a rare, long-term, systemic disorder that involves the formation of granulomas and inflammation of blood vessels (vasculitis). It is an autoimmune disease and a form of vasculitis that affects small- and medium-sized vessels in many organs, but most commonly affects the upper respiratory tract, lungs, and kidneys...