Granulomatous vasculitides and vasculitides with extravascular granulomatosis

Vasculitides are inflammatory diseases of blood vessels caused by autoimmune or infectious processes, which are associated with alterations and destruction of the vascular wall. From a histopathological point of view, granulomatous vasculitides can be distinguished from necrotizing vasculitides with respect to the pattern of inflammation. Granulomatous vasculitides are characterized by intramural, predominantly lymphohistiocytic infiltrates with the formation of giant cells. They include giant cell arteritis (GCA) and Takayasu arteritis (TAK). By contrast, anti-neutrophil cytoplasmic autoantibody (ANCA)-associated vasculitis (AAV) belongs to the group of necrotizing vasculitides. AAV includes granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), and eosinophilic granulomatosis with polyangiitis (EGPA). In addition to systemic necrotizing small vessel vasculitis, GPA and EGPA are characterized by extravascular granulomatous necrotizing inflammation mainly affecting the upper and/or lower respiratory tract, in EGPA with eosinophilic infiltrates. These granulomatous lesions are part of the autoimmune process and associated with tissue damage.