We describe a 32-year-old patient with adult dermatomyositis who developed dyspnea and worsening of pre-existing infarcted skin lesions of the fingers. Chest radiographs showed diffuse hazy reticulonodular infiltration in both lungs, subcutaneous emphysema, pneumomediastinum, and pneumothorax. The pulmonary symptoms and cutaneous lesions gradually improved with a high dose of prednisolone. Although subcutaneous emphysema and pneumomediastinum occur frequently in association with traumatic disruption of cutaneous and mucosal barriers and assisted ventilation, it has rarely been observed in patients with interstitial pneumonitis in connective tissue diseases. Although dermatomyositis and subcutaneous emphysema are all relatively well-known diseases to dermatologists, the occurrence of spontaneous pneumomediastinum and pneumothorax and subsequent subcutaneous emphysema in connective tissue diseases such as dermatomyositis is unfamiliar. We discuss the possible mechanisms of this condition.