Distribution of vessel involvement by large-, medium-, and small-vessel vasculitis

Distribution of vessel involvement by large-vessel vasculitis, medium-vessel vasculitis, and small-vessel vasculitis. Note that there is substantial overlap with respect to arterial involvement, and an important concept is that all three major categories of vasculitis can affect any size artery. Large-vessel vasculitis affects large arteries more often than other vasculitides. Medium-vessel vasculitis predominantly affects medium arteries. Small-vessel vasculitis predominantly affects small vessels, but medium arteries and veins may be affected, although immune-complex small-vessel vasculitis rarely affects arteries. Not shown is variable-vessel vasculitis, which can affect any type of vessel, from aorta to veins. The diagram depicts (from left to right) aorta, large artery, medium artery, small artery/arteriole, capillary, venule, and vein.