Micropolyangiitis

Microscopic polyangitis (MPA) is a small vessel involvement type systemic vasculitis. The clinical manifestations are similar to PAN, and are characterized by rapid glomerulonephritis (RPGN) and lung involvement, which is different from PAN. Classical PAN mainly invades the small and medium arteries. If the lesion involves smaller arterioles and capillaries, classic PAN is excluded and classified as MPA. Its clinical features are pulmonary-renal vasculitis and serum anti-MPO positive.