The prognosis of interstitial pneumonia in patients with dermatomyositis is thought to depend on the histologic type and response to therapy. We report a case of hypomyopathic dermatomyositis with rapid development of a fatal interstitial pneumonia. Although the histology of lung biopsy indicated minimal alveolitis, the patient died despite multi-immunosuppressive therapy. The autopsy revealed acute and organizing diffuse alveolar damage. In this case, the lung biopsy taken before the acute deterioration did not predict the patient's poor prognosis. Interstitial pneumonia in patients with amyopathic or hypomyopathic dermatomyositis would develop rapidly progressive and refractory. We need larger and better prospective studies to determine whether early and intensive immunosuppressive therapy improves the prognosis of interstitial pneumonia in patients with amyopathic or hypomyopathic dermatomyositis.