To evaluate the long-term outcome of patients with anti-myeloperioxidase (MPO) anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis, the impact of addition of an intravenous pulse cyclophosphamide therapy to a daily oral corticoid therapy was assessed in 20 patients for 5 years. No patient diagnosed with Wegener\u27s granulomatosis was included in this study. Ten patients received corticosteroid treatment alone (OCS group) and 10 patients were treated with corticosteroid and cyclophosphamide in combination (CYC group). Four patients in CYC group, survived their renal function without dialysis. Three of 6 patients that required dialysis therapy, died of gastric ulcer, thrombocytopenia probably due to cyclophosphamide, and cardiac failure. Two of 10 patients in OCS group did not need dialysis therapy. Five (50%) of these patients died and 3 (30%) received dialysis therapy. Three patients died of pulmonary hemorrhage, one died of colon cancer, and one died of cardiac failure. At the diagnosis, no significant differences in the levels of serum creatinine and MPO-ANCA titer, sex ratio and ages were observed between two groups. However, the retrospective analysis revealed that 1) the patients who survived for 5 years without dialysis therapy irrespectively of two types of therapy were all women, 2) the levels of MPO-ANCA at 3 months after the initiation of treatment were significantly higher (p＜0.05) in patients treated with corticosteroids alone than those with combination therapy, and that 3) the scores of renal histopathology (glomerular sclerosis and interstitial fibrosis) were significantly higher in patients who failed to survive than those who succeeded to survive without dialysis therapy. From these results, it is suggested that the combination therapy with corticosteroids and cyclophosphamide might be effective for improvement of life and renal survival of patients with MPO- ANCA-associated vasculitis. Moreover, the values of MPO-ANCA should be evaluated after the start of the therapy
