Granulomatosis with polyangiitis (GPA) and microscopic polyangiitis (MPA) are two major clinical entities recognized among ANCA-associated vasculitides. GPA and MPA differ in the presence or absence of granuloma, organ involvement, and risk of relapses.
GPA is more often, but not exclusively, associated with proteinase 3 (PR3)-ANCA, and MPA is more often, but not exclusively, associated with myeloperoxidase (MPO)-ANCA.