We describe a 53-year-old patient with dermatomyositis, who developed pneumatosis intestinalis (PI) accompanied by pneumoperitoneum, pneumoretroperitoneum, pneumomediastinum, and subcutaneous emphysema of the neck. The development of PI in our patient was possibly attributed to the effect of factors such as dermatomyositis, corticosteroids, methotrexate, and alpha-glucosidase inhibitor (AGI). The coexistence of multiple factors associated with PI might enhance the risk of developing PI, even though each of them alone is not sufficient to induce it. In particular, the use of AGIs for patients treated with immunosuppressive agents such as corticosteroids requires evaluation.