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 phosphocreatine (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.