[Two cases of classical polyarteritis nodosa associated with MPO-ANCA].

Case 1: An 82 year-old female had a drop-foot, livedo reticularis and paresthesia. MPO-ANCA was positive. Because of developing renal dysfunction, she underwent steroid pulse therapy and dialysis, but died from the complication of congestive heart failure. Autopsy revealed necrotizing arteritis in the interlobular arteries and the arcuate arteries of the kidneys. Crescent formation was not found in the glomeruli. Case 2: A 49-year-old male had a drop foot and numbness. MPO-ANCA was positive. Because of developing renal failure, he underwent dialysis and steroid pulse therapy. MPO-ANCA became negative. Nevertheless, he developed perforation of multiple ulcers in the small intestine and died. Pathohistology revealed arteritis in medium-size arteries at the branch level of the mesenteric arteries. Since the presented two cases showed rapidly and irreversibly aggravated renal function with positive MPO-ANCA, MPA was suspected. However, pathological findings from the autopsy and operation and not the kidney biopsy supported the diagnosis of polyarteritis nodosa (PN). Vasculitis in the arterioles was absent. MPO-ANCA is not specific, and it can be detected in not only MPA, but also PN. The clinical course and pathological findings must be considered to differentiate PN from MPA.