To determine the prognostic value of galectin‐9 and CXCL10 during clinical follow‐up in patients with juvenile DM, we measured the biomarkers in a prospective cohort of 28 patients, with a median follow‐up time of 2.8 years per patient (the characteristics of these patients are listed in Supplementary Table 6 [http://onlinelibrary.wiley.com/doi/10.1002/art.40881/abstract]). The gene discussed is CXCL10; the disease is dermatomyositis.