P-31 MAGNETIC-RESONANCE SPECTROSCOPY IN POLYMYOSITIS AND DERMATOMYOSITIS - ALTERED ENERGY-UTILIZATION DURING EXERCISE

Objective. To explore alterations in energy utilization as a potential etiology for weakness in polymyositis and dermatomyositis (PM/DM). Methods. P-31 magnetic resonance spectroscopy studies were performed in patients with acute and treated PM/DM and in normal controls, at rest and with exercise. Results. Patients with acute and treated PM/DM showed increased ratios of inorganic phosphate to phosphocrcatine (PCr) during exercise, with loss of ATP disproportional to loss of PCr. Conclusion. This study demonstrates changes in energy utilization in PM/DM, thus supporting the notion of a metabolic etiology for the weakness associated with these diseases.