Magnetic resonance imaging and p‐31 magnetic resonance spectroscopy provide unique quantitative data useful in the longitudinal management of patients with dermatomyositis

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Abstract
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, were found in 10 patients. In some individuals, bioenergetic defects preceded other changes and persisted after resolution of inflammation. In general, clinical impressions correlated with MRI/MRS data. Conclusion. MRI and MRS provide unique data which are quantitative and which cannot be obtained from routine laboratory tests. These MR evaluations appear to be of value in assessing the status of DM patients during treatment with steroids and immuno-suppressive drugs.