A Case of a Small Cell Lung Cancer Patient with Anti-transcriptional Intermediary Factor 1γ Antibody Who Developed Dermatomyositis after Successful Chemoradiotherapy

We herein report a 63-year-old woman with small-cell lung cancer (SCLC) who developed dermatomyositis (DM) after initial chemoradiotherapy despite tumor reduction. Serum anti-transcriptional in termediary factor (TIF) 1γ antibody was detected before the development of DM, and its levels increased over time. She died five months after the diagnosis of SCLC. Anti-TIF1γ antibody is known to be a marker for cancer-associated DM (CAM); however, the present case indicates that the antibody can be found in cancer patients without DM. This case is also unusual, as DM developed later despite successful chemoradiotherapy.