[Clinical features of pulmonary involvement in patients with microscopic polyangiitis]

To explore the clinical features of pulmonary involvement in patients with microscopic polyangiitis (MPA).

We retrospectively investigated the clinical data of 50 patients hospitalized with MPA in Peking Union Medical College Hospital from January 2008 to December 2009, the data included clinical manifestation, laboratory parameters, echocardiography, pulmonary function test, chest computed tomography, and histopathology of kidney.

Pulmonary involvements were observed in 46 patients, common symptoms include cough (34/46), expectoration (30/46), dyspnea (19/46) and hemoptysis (16/46). Pulmonary involvement was the initial manifestation in 14 patients, five cases had radiographic evidences of usual interstitial pneumonia before MPA was diagnosed. The prevalence of positive MPO-ANCA antibodies in MPA patients was 96%. The prevalence of positive PR3-ANCA antibodies was 6%. Radiographic manifestations included ground glass attenuation (16/37), interstitial changes (16/37), infiltrates (12/37) and pleural effusion (7/37). The most frequent abnormality in pulmonary function test was reduced carbon monoxide diffusing capacity (12/15) and restrictive ventilation dysfunction (4/15). The incidences of pulmonary hypertension was 33% (13/39), the average pulmonary artery systolic pressure was (48 ± 8) mm Hg (1 mm Hg = 0.133 kPa).

The prevalence of pulmonary involvement in patients with MPA was high, pulmonary involvement was the initial manifestation in 28% patients. The clinical manifestations were nonspecific, radiographic manifestations included ground glass attenuation, interstitial changes, infiltrates and pleural effusion. The short term prognosis was well in patients with pulmonary involvement treated with systemic corticosteroids and cyclophosphamide, infection was a leading cause of death in patients with pulmonary involvement.