To determine whether defects of skeletal muscle oxidative phosphorylation can be differentiated from other causes of skeletal muscle weakness by aerobic responses to exercise, 10 patients with oxidative phosphorylation abnormalities (n = 5) or defects of contractile element apparatus or peripheral neuropathy (n = 5) underwent bicycle exercise testing. Results were compared with 16 healthy control subjects. The response of oxygen consumption to work rate and ventilatory threshold were significantly reduced in the oxidative phosphorylation group when compared to subjects with other causes of muscle weakness and the control group. Exercise testing appears to be useful in distinguishing patients with defects of oxidative phosphorylation from those with other causes of skeletal muscle weakness.
The authors are with the Department of Pediatrics, Divisions of Cardiology and Neurology at Wayne State University School of Medicine, Children’s Hospital of Michigan, 3901 Beaubien, Detroit, MI 48201