[Mixed connective tissue disease-associated interstitial pneumonia complicated by pneumomediastinum during prednisolone therapy].

A 59-year-old woman was admitted to our hospital with exertional dyspnea. Linear and reticular opacities in the middle and lower fields of both lungs were observed on chest roentgenograms and chest computed tomograms (CT). The presence of anti RNP-antibody and Raynaud's phenomenon, sclerosis of the fingers, and leukopenia yielded a diagnosis of mixed connective tissue disease associated with interstitial pneumonia. The symptoms and lung involvement were alleviated after the administration of prednisolone (40 mg/day). However, the patient experienced the sudden onset of dyspnea during pulmonary function tests. A chest X-ray film disclosed mediastinal air around the left pulmonary artery, and a chest CT scan demonstrated some blebs in the left lower lung field. After tapering the dosage of prednisolone in 5 mg increments per week, the pneumomediastinum disappeared without treatment. The clinical features and laboratory data findings suggested the patient's interstitial pneumonia was associated with systemic lupus erythematosus rather than with progressive systemic sclerosis or dermatomyositis. The pneumomediastinum may have been due to the rupture of blebs secondary to interstitial pneumonia during pulmonary function tests or as a result of steroid therapy.