Both cross‐sectionally and longitudinally, galectin‐9 and CXCL10 outperformed the currently used laboratory marker, creatine kinase (CK), in distinguishing between juvenile DM patients with active disease and those in remission (area under the receiver operating characteristic curve [AUC] 0.86–0.90 for galectin‐9 and CXCL10; AUC 0.66–0.68 for CK). The gene discussed is CXCL10; the disease is dermatomyositis.