Anti-EJ Antibody-positive Anti-synthetase Syndrome Associated with Retroperitoneal Sarcoma

A 74-year-old man with interstitial lung disease (ILD) underwent surgical excision of a growing retroperitoneal tumor and was diagnosed with spindle cell sarcoma. Just after the surgery, skin eruption and muscle weakness emerged. Based on his symptoms and examination findings, we diagnosed him with anti-synthetase syndrome (ASS) with positive anti-glycyl-transfer ribonucleic acid synthetase antibody (anti-EJ) as paraneoplastic syndrome. Immunosuppressive treatments kept his progressing ILD stable for 21 months, although an expanding lung metastatic lesion from primary sarcoma was detected. Measurements of myositis-specific antibodies may enable the prediction of the efficacy of immunosuppressive treatments for paraneoplastic syndrome, even if the primary disease becomes progressive.