Progressive obstructive lung disease associated with microscopic polyangiitis.

Small airway involvement and progressive severe airflow obstruction are unexpected features in patients with microscopic polyangiitis. We report the case of a patient with microscopic polyangiitis and circulating anti-neutrophil cytoplasmic antibodies (ANCA), who developed pulmonary hyperinflation and airflow obstruction over a 7-yr period. Systemic manifestations of this vasculitis improved under corticosteriods and cyclophosphamid therapy, a treatment that did not influence either the very high level of anti-myeloperoxidase antibodies or the ventilatory impairment. Small airway involvement was suspected on the basis of pathologic small airway lesions and a mild emphysematous pattern on computed tomography (CT) scan, which was out of proportion with the severity of the obstructive lung disease.