Amyopathic dermatomyositis (ADM) is recognized as a variant phenotype of dermatomyositis and characterized by typical skin manifestations without evidence of muscular inflammation. While interstitial lung disease (ILD) is occasionally found as one of the lung manifestations in ADM patients, the development of a pneumomediastinum and/or subcutaneous emphysema in this disease entity is one of the extremely rare pulmonary complications. These latter complicated pulmonary manifestations have been usually reported in idiopathic ADM with ILD without any other associated medical conditions. We report a case presented with the spontaneous pneumomediastinum and subcutaneous emphysema in both ADM and cryptogenic organizing pneumonia during adjuvant chemotherapy based on cyclophosphamide for breast cancer.