Clinical Features of Microscopic Polyangiitis: A Cohort Study in a Southern Taiwan Medical Center

BACKGROUND: To determine the clinical features and outcomes of microscopic polyangiitis (MPA) in Taiwanese patients, we retrospectively reviewed the medical records of patients diagnosed with MPA at a single medical center in Taiwan between January 1, 1996 and June 1, 2011. METHODS: A cohort of 21 patients (17 men and 4 women) with a mean age of 67 ± 11 years was investigated. Diagnosis was made according to the Chapel Hill criteria for MPA. All patients had renal histological evidence of microscopic polyarteritis. RESULTS: The main clinical manifestations were renal involvement (100%), lung involvement (67%), gastrointestinal involvement (24%), skin lesion (15%), fever (15%), mononeuritis multiplex (10%), and arthralgia (15%). Antineutrophil cytoplasmic antibodies were present in 18 of the 21 patients (86%). Seventeen patients were treated with steroids and cyclophosphamide. Eleven of these 17 patients had stable or improved courses. Ten of the 21 patients (47.6 %) received dialysis at the time of diagnosis and two of them recovered to achieve a dialysis-independent status. Renal survival rates were 46.1% at 1 year and 36.9% at 3 years. A good renal function at diagnosis, lower chronic kidney biopsy index, and good response to treatment were associated with better renal outcome. Patient survival rates were 73.8% at 1 year and 58.7% at 3 years. CONCLUSION: Taiwanese patients with MPA were older, and had a high rate of lung involvement, all of which are indicators of a poor prognosis. Our study suggests that birmingham vasculitis activity score may be a better prognostic predictor in the evaluation of MPA patients. For patients with renal failure, rapid confirmation with renal biopsy and early treatment may improve outcome.