Objective. To evaluate the utility of magnetic resonance imaging (MRI) and P-31 magnetic resonance spectroscopy (MRS) in the longitudinal management of patients with dermatomyositis (DM).Methods. The study group consisted of 11 patients, including 3 children, all of whom had a clinical diagnosis of DM. A control group of 8 subjects was studied simultaneously. MRI included images as well as calculations of T1 and T2 relaxation times. The P-31 MRS protocol evaluated metabolic status (i.e., inorganic phosphate/phosphocreatine ratios and phosphocreatine and ATP levels) during rest, exercise, and recovery.Results. T2-weighted images of the thigh muscles showed inflammation even when serum creatine phosphokinase levels were in the normal range. Metabolic abnormalities, which were accentuated with exercise,

Objective. To investigate the use of magnetic resonance imaging (MRI) and P-31 magnetic resonance spectroscopy (MRS) in characterizing the metabolic and functional status of muscles in patients with amyopathic dermatomyositis (DM) and to compare the findings with those in patients with classic myopathic DM.Methods. Nine patients with amyopathic DM, 11 patients with myopathic DM, and 11 normal individuals were studied. MRI images of thigh muscles were obtained, and T1 and T2 relaxation times were calculated. Biochemical status was quantitated with P-31 MRS, by determining concentrations of phosphate metabolites during rest and exercise.Results. Patients with amyopathic DM showed no muscle inflammation, and MRS data obtained during rest were normal. During exercise at 25% and 50% maximum voluntary contractile force, the MRS data revealed significant differences between amyopathic DM patients and control subjects indicating inefficient metabolism. In contrast, muscles of patients with myopathic DM showed inflammation and metabolic abnormalities even during rest.Conclusion. Metabolic deficiencies in patients with amyopathic DM were unmasked by exercise, sug-

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