Intracellular phosphates in inclusion body myositis--a 31P magnetic resonance spectroscopy study.

Muscle phosphorus magnetic resonance spectroscopy was used to study oxidative metabolism at rest and during recovery from exercise in 7 patients with sporadic inclusion body myositis (s-IBM), compared with normal controls (n=8) and mitochondrial myopathies (n=20). At rest, 6/7 patients had elevated inorganic phosphates. Recovery parameters were not different from controls, in contrast with mitochondrial myopathies, who showed abnormal rest and recovery. The normal recovery suggests that mitochondrial oxidative capacity is not impaired in s-IBM.