Moneta GM, et al. - In this investigation, researchers assessed the expression of type I interferon (IFNα/β)– and type II IFN (IFNγ)–inducible genes in muscle biopsy specimens from juvenile dermatomyositis (DM) patients and correlated their levels of expression with histologic and clinical characteristics. From patients with juvenile DM (n = 39), patients with Duchenne's muscular dystrophy (DMD), and healthy controls, expression levels of IFN-inducible genes and proinflammatory cytokines were evaluated by a quantitative polymerase chain reaction in muscle biopsy specimens. Compared to DMD patients and healthy controls, muscle expression levels of IFNα/β-inducible genes, IFNγ, IFNγ-inducible genes, and tumor necrosis factor (TNF) were significantly higher in juvenile DM patients not receiving glucocorticoid therapy before muscle biopsy. According to findings, increased muscle expression of IFN-inducible genes in juvenile DM patients and their association with histological and clinical characteristics further support a pathogenic role in juvenile DM for both type I and type II IFNs.