Anti-EJ antibody-positive interstitial pneumonia with breast cancer improved by combining immunosuppressive therapy and chemotherapy.

We present a case of a 45-year-old woman diagnosed with interstitial pneumonia (IP) during a comprehensive breast cancer evaluation. Although the patient showed no obvious clinical symptoms of polymyositis or dermatomyositis, the presence of anti-glycyl-transfer ribonucleic acid synthetase antibodies confirmed anti-synthetase syndrome. The patient began methylprednisolone for treatment of the IP. She then received preoperative chemotherapy with epirubicin and cyclophosphamide before undergoing a mastectomy. A significant improvement was seen in the patient's IP during treatment. This case emphasizes the potential advantages of personalized immunosuppressive therapy for patients who are simultaneously diagnosed with anti-synthetase syndrome and cancer.