Idiopathic inflammatory myopathies evaluated by near infrared spectroscopy

In this study we evaluated whether near-infrared spectroscopy (NIRS) can determine the metabolic patterns of dermatomyositis (DM), polymyositis (PM), and inclusion-body myositis (IBM).We enrolled 10 consecutive patients affected by DM, 11 by PM, and 9 by IBM, and 3 groups of healthy controls. We measured changes in oxygenated and deoxygenated hemoglobin/myoglobin in the extensor digitorum communis during venous and arterial occlusion testing (VOT) and post-occlusion hyperemia.DM showed lower oxygen consumption (P=0.04) during VOT and reduced oxygen supply after VOT (P=0.04) compared with controls. IBM patients showed higher oxygen consumption (P=0.04) during VOT and higher oxygen supply after VOT (P=0.03) than controls. DM patients showed reduced oxidative metabolism compared with IBM (P=0.001), and an impaired ability to supply oxygen compared with PM (P=0.03) and IBM (P=0.001) patients.NIRS differentiated samples of DM and IBM patients from controls, but it could not distinguish PM patients from a sample of healthy subjects.