what is microscopic polyangiitis
Microscopic polyangiitis (also known as microscopic polyarteritism, Microscopic polyarteritis nodosa, MPA) is an ill-defined autoimmune disease characterized by a systemic, pauci-immune, necrotizing, small-vessel vasculitis without clinical or pathological evidence of necrotizing granulomatous inflammation.igns and symptoms [edit]. Clinical features may include constitutional symptoms like fever, loss of appetite, weight loss, fatigue, and kidney failure. A majority of patients may have blood in the urine and protein in the urine. Rapidly progressive glomerulonephritis may occur.