Pneumomediastinum in a patient with microscopic polyangiitis preceded by interstitial pneumonia

A 73-year-old woman was diagnosed with interstitial pneumonia in 2006; however, the disease was not progressive. Four years later, purpura, peripheral neuropathy, and increased levels of myeloperoxidase anti-neutrophil cytoplasmic antibodies (583 EU/mL) and C-reactive protein (2.27 mg/dL) were observed, and a diagnosis of microscopic polyangiitis was made. Treatment with prednisolone and azathioprine was initiated. However, on the 35th hospital day, chest computed tomography showed pneumomediastinum and subcutaneous emphysema without aggravation of the interstitial pneumonia. To our knowledge, this is the first report of pneumomediastinum as a complication of microscopic polyangiitis associated with interstitial pneumonia.