PRTN3 and granulomatosis with polyangiitis: GPA, formerly known as Wegener's granulomatosis, is a primary systemic small-vessel vasculitis, which typically produces granulomatous inflammation of the upper and lower airways, necrotizing glomerulonephritis in the kidneys, and is associated with a cytoplasmic pattern of antineutrophil cytoplasmic antibodies (cANCA), with specificity against proteinase-3 (PR3).