A 49-year-old man was admitted to our hospital with fever, general fatigue, muscle pain in the neck, and exertional breathlessness. We initiated treatment with ciprofloxacin and methylprednisolone at 1 mg･kg⁻¹･day⁻¹; however, this failed to improve his respiratory symptoms. We diagnosed the patient with rapid progressive interstitial pneumonia (RPIP) with 22 dermatomyositis on the basis of the findings of diffuse alveolar damage (DAD) on chest computed tomography; mild proximal muscle weakness and pain; elevated levels of myogenic enzymes, C-reactive protein (CRP) levels, and erythrocyte sedimentation rate (ESR); the myogenic pattern on the electromyogram; malar rash; erythema of the inner canthus; and subungual and splinter hemorrhage. We initiated steroid pulse therapy, cyclophosphamide pulse therapy, and continuous infusion therapy with cyclosporine; however, the patient required mechanical ventilation on day 9 and died on day 12 after admission. Lung autopsy revealed pathological exudative and organizing phases of diffuse alveolar damage, and the anti-CADM-140 antibody was found in the patient's serum. Occasionally, amyopathic dermatomyositis is complicated by RPIP, which manifests as characteristic cutaneous lesions. However, in this case RPIP was accompanied by dermatomyositis characterized by the anti-CADM-140 antibody with only atypical cutaneous lesions. Therefore this case was thought to be very rare. Moreover, initial diagnosis of it as RPIP accompanied by dermatomyositis was difficult. This case indicates the importance of anti-CADM-140 antibody in interstitial pneumonia with atypical cutaneous lesions.