The number of MDA5+ DM patients who did not receive any therapy (n = 9, CMV-IgM+n = 6, CMV-IgM−n = 3) was too small to facilitate informative lymphocyte subset analysis; thus, we performed the same analysis in postmatched MDA5+ DM patients (n = 34; see Supplementary Table 3 for further details). Here, IFIH1 is linked to dermatomyositis.