Abstract: Objective: To get to know the clinical features of dermatomyositis（DM） complicated by subcutaneous emphysema and pneumomediastinum and the influence of pneumomediastinum on patients′ hemodynamic status. Methods: The clinical features of 6 hospitalized DM patients complicated by pneumomediastinum as well as 7 similar patients with clinical data in literatures were analyzed. Results: Typical rashes were found in all patients,with cutaneous vasculitis in 61% of the cases,normal muscle strength in 54%,normal CK in 69%,and increasing LDH in 92%.Interstitial lung changes were found before or while the complication was present,and steroids were in use in all the cases.Although no heart disease histories were recorded,cardiac vascular symptoms were found in 38% of the cases.The mortality rate was as high as 53%. Conclusion: DM patients with interstitial lung changes,cutaneous vasculitis,normal or mild myositis and CK and increased LDH were at the risk of pneumomediastinum.The prognosis of such a complication was worse with high mortality rate.