A variety of myositis-specific autoantibodies (MSAs) have been detected in patients with dermatomyositis (DM). We analyzed MSAs in 20 cases with DM. Eleven of the 20 cases were positive. Out of those 11 cases, 3 were positive for antibodies against aminoacyl-tRNA synthetase and 3 had antibodies to anti-melanoma differentiation-associated gene 5 detected using an immunoprecipitation assay and/or a specific enzyme-linked immunosorbent assay. One case had anti-NXP-2 antibodies and 4 cases had anti-transcriptional intermediary factor 1 (TIF1)-α/γ antibodies detected by immunoprecipitation and Western blotting. Two of those 4 cases had antibodies for both TIF1-α and TIF1-γ, and the 2 other cases had antibodies for TIF1-γ alone. We report the 2 cases with antibodies for TIF1-γ only, who were young-adult females without an internal malignancy or interstitial pneumonia. Those 2 cases had clinically amyopathic DM. Among DM patients with antibodies against TIF1 family proteins, there seems to be a subgroup of young-adult cases who have clinically amyopathic DM and show good prognosis without malignancy.