NADH dehydrogenase (NDUFA4 and NDUFB4), ATP synthase (ATP5O and ATP5B) and cytochrome c oxidase (COX) family (COX5B, COX6A2 and COX7C) are crucial molecules involved in the oxidative phosphorylation in mitochondrial metabolism, and the decreased levels of these molecules suggested a crucial role of impaired mitochondrial phosphorylation and lower oxidative capacity in the pathogenesis of JDM, accounting for the extremity weakness in JDM patients. This evidence concerns the gene COXFA4 and juvenile dermatomyositis.