ABSTRACT
Microscopic polyangiitis (MPA) is a multisystem autoimmune vasculitis, associated
with antineutrophil cytoplasm antibodies (ANCA), and characterized by pauci-immune
necrotizing vasculitis of small blood vessels. It is one of three small vessel vasculitidies
commonly associated with ANCA, the others being Wegener’s granulomatosis (WG)
and Churg-Strauss syndrome (CSS). However, despite the common association with
ANCA, these disease entities have significant differences in their clinical fea-
tures and possibly in their underlying pathophysiology. As such, data on pathological
mechanisms should be extrapolated from one disease to another with caution.
