Microscopic polyangiitis (MPA)
What is MPA? How does it differ from classic polyarteritis nodosa (PAN) and Granulomatosis with polyangiitis (GPA)?
MPA is defined as a systemic necrotizing vasculitis that clinically and histologically affects small vessels (i.e., capillaries, venules, or arterioles) with few or no immune deposits. Frequently it is associated with focal segmental necrotizing GN and pulmonary capillaritis.
It can be separated from classic PAN primarily because it does not cause microaneurysm formation of abdominal or renal vessels. It can be differentiated from GPA in that it does not cause granuloma formation or a granulomatous vasculitis
