oa Metabolic Myopathies: Diagnosis and Treatment

Metabolic myopathy is referred to a rare group of inherited muscle diseases caused by specific enzymatic defects that lead to muscle energy defect and subsequently muscle dysfunction. They are divided into disorders of carbohydrate metabolism, disorders of lipid metabolism and mitochondrial disorders. Examples of the common metabolic myopathies are Pompe disease, McArdle’s disease, beta-oxidation defects and carnitine disorders. A unique clinical presentation should raise the suspicion of such rare muscle disorders specially when the patient has episodic muscle dysfunction and dynamic rather than static symptoms. Premature exertional fatigue and exercise-associated muscle cramps are other clues. However, they occasionally present as progressive muscle weakness mimicking dystrophic muscles disorders or multiorgan involvement. Early diagnosis and implementation of therapeutic strategy will help prevent acute muscle dysfunction, myoglobinurea and rhabdomyolysis. This strategy may include avoiding vigorous exercise and prolonged fasting, eating complex carbohydrates, carnitine and MCT supplementation and enzyme replacement therapy.