De Paepe B, et al. - Given the link of cytokine growth differentiation factor-15 (GDF-15) with inflammatory and mitochondrial disease, researchers examined its expression in myositis patients. Using enzyme-linked immunosorbent assays, they assessed GDF-15 protein levels in 35 idiopathic inflammatory myopathy (IIM) serum samples. These were compared with levels measured in samples from healthy people and from patients having genetically confirmed hereditary muscular dystrophies and mitochondrial disorders. Compared with healthy controls, significantly higher levels of GDF-15 protein were detected in IIM sera. Raised GDF-15 protein levels in IIM muscle were confirmed on western blotting. The upregulation of GDF-15, a myokine, in myositis was shown for the first time ever in this study, and the cytokine was presented as a potential diagnostic serum biomarker.