label: Microscopic Polyarteritis
label_lc: microscopic polyarteritis
description: A systemic necrotizing vasculitis that typically affects the small and medium-sized muscular arteries. In some cases, however, microscopic vessels are also affected (e.g., in the kidneys), a condition that has been called microscopic polyarteritis or polyangiitis; this disorder is felt to be more closely associated with Wegener granulomatosis than to classic polyarteritis nodosa.