Risk Factors Associated with Relapse in Japanese Patients with Microscopic Polyangiitis

Objective. We retrospectively studied the risk factors associated with relapse during remission maintenance therapy for myeloperoxidase-antineutrophil cytoplasmic autoantibody (MPO-ANCA)-positive microscopic polyangiitis (MPA). Methods. Sixty-two patients diagnosed with MPA according to the European Medicines Agency classification algorithm during a 2-year period from January 1, 2005, to December 31, 2006, and who achieved remission after the first remission-induction therapy, were examined (registration no. UMIN000001785). Results. The patient group comprised 25 men and 37 women aged 70.0 +/- 8.9 years. The mean observation period was 30.2 +/- 15.9 months. The rate of relapse was 24.2% (15/62), and mean interval between remission and relapse was 16.9 +/- 13.5 months. During maintenance therapy following remission, the risk of relapse increased when the reduction rate of prednisolone increased above 0.8 mg/month (OR 12.6, 95% CI 2.2-97.9). Proteinuria at the start of maintenance therapy (regression coefficient 1.991 +/- 0.758, p < 0.05) and the change in red blood cell counts in urine during the period from the start of maintenance therapy to the final observation (regression coefficient 0.126 +/- 0.040, p < 0.01) were identified as risk factors influencing the vasculitis damage index. Conclusion. In Japan, relapse of MPO-ANCA-positive MPA may be associated with the reduction rate of oral prednisolone administration during maintenance therapy. (First Release Dec 15 2011; J Rheumatol 2012;39:545-51; doi:10.3899/jrheum.110705)