Active DM patients had higher level of IFN-β (4.58 [0.0-30.7]) compared to non-active DM patients (0 [0-0] pg/ml, p=0.0001) with an AUC at 0.71 (IC95 0.61-0.81; p<0.05) because of a lot of false negative. This evidence concerns the gene IFNB1 and dermatomyositis.