Development of microscopic polyangiitis in patients with chronic airway disease.

Microscopic polyangiitis (MPA) is a rare systemic vasculitis syndrome, which is often accompanied by positive myeloperoxidase-specific antineutrophil cytoplasmic antibody (MPO-ANCA). While pulmonary involvement of MPA consists mainly of diffuse alveolar hemorrhage and interstitial pneumonia, bronchiectasis has been reported as a pulmonary lesion in association with MPA. To investigate the clinical features of patients with MPA, focusing on the presence or the absence of preceding chronic airway diseases (CAD), we conducted a retrospective observational study of 26 patients in the last 13 years at Saga University Hospital. The clinical records and radiologic chest examinations were reviewed retrospectively. Pulmonary manifestations were alveolar hemorrhage in 3 patients (12%) and interstitial pneumonia in 5 (19%). Bronchiectasis, defined by the findings of chest radiograph and computed tomography, was found in 9 patients (35%). Four patients (15%) with bronchiectasis and one patient (4%) with chronic bronchitis had experienced chronic bronchial suppuration prior to the onset of MPA. Ten patients were classified as having chronic airway disease (CAD) before the onset of MPA. MPO-ANCA tended to be lower in the CAD group than in the non-CAD group. None of the patients in the CAD group had pulmonary hemorrhage or interstitial pneumonia. Only one patient (10%) in the CAD group died within 90 days of the onset of MPA, while 7 (43.8%) of the non-CAD group died. Our study suggests that MPA may result in part from CAD and that the clinical course of MPA with CAD may be different from MPA without CAD.