Objective To study the clinical manifestations,diagnosis,treatments and prognosis of the pulmonary change in mixed connective tissue disease(MCTD).Methods From January 1996 to June 2008,112 patients with definite MCTD in Second Affiliated Hospital of Harbin Medical University were retrospectively studied,and the clinical feature about pulmanary manifestations,echocardiography feature,radiology features and treatments were reviewed and analyzed.44 patients were followed up.Results 48(5 male)had pulmonary manifestation.The median age of onset of symptoms was 39 years and the median duration of disease was three years.The most common manifestation was pleural effusion and(or)pachynsis pleurae(21 cases,18.8%).16 patients(14.3%) had interstitial lung disease,and 8 cases(7.1%)had pulmonary hypertension.The cardinal symptom was short breath.Thirteen patients(11.6%)had dyspnea,4 cases(3.6%)had chest pain,and 4 cases(3.6%)had cough.Reductions of pulmonary function or abnormalities of ultrasonographic image were noted in 25(52.1%)of 48 patients with pulmonary involvement of MCTD who had not any complaint of respiratory symptoms.Six patients had reductions in diffusing capacity of the lung for carbon monoxide(DLCO),17 patients had pulmonary abnormality on chest X ray or CT,and two patients had pulmonary hypertension on doppler echocardiography.Conclusion Pulmonary involment of MCTD may contribute to prognosis seriously.DLCO was the most sensitive parameter.Pulmonary hypertension was the most common cause of death.