Myopathies caused by disorders of lipid metabolism.

Myopathies due to abnormalities in fatty acid oxidation fall into several clinical categories. Rhabdomyolysis occurring with prolonged stress on the muscle is frequently found to be caused by carnitine palmityl transferase deficiency. The association of systemic metabolic derangements and muscle weakness is seen with defects in long-chain acyl-CoA dehydrogenase, medium-chain acyl-CoA dehydrogenase, or short-chain acyl-CoA dehydrogenase. The latter three are often associated with low muscle carnitine concentrations. In patients who present with only muscle weakness and triglyceride storage, muscle carnitine concentrations may be either normal or reduced.