. 2012 Mar 6;184(4):426–430. doi: 10.1503/cmaj.110518

Table 1:

Metabolic myopathies causing recurrent-episode rhabdomyolysis

Characteristic	Disorders of fatty acid β-oxidation	Muscle glycogenoses	Mitochondrial diseases
Prevalence	Varies with type MCAD 1/10 000⁸^,⁹ Others less common except in certain populations	Varies with type McArdle disease 1/100 000⁸^,⁹ Others less common	1/8000⁸^,⁹
Inheritance pattern	Most are autosomal recessive⁸^,⁹	Most are autosomal recessive⁸^,⁹	Any pattern of inheritance is possible: maternally inherited through mitochondrial DNA or inherited through nuclear DNA in autosomal dominant or recessive or X-linked fashion⁸^,⁹
Duration of exercise needed to trigger symptoms	Longer duration (> 30 min) ⁸^,⁹	Shorter duration (< 30 min) ⁸^,⁹	Variable⁸^,⁹
History of second-wind phenomenon^*	No	Often present⁸^,⁹	Not usually present⁸^,⁹
Creatine kinase levels	Normal between episodes of symptoms⁸^,⁹	Elevated even between episodes of symptoms⁸^,⁹	Variable; may be normal⁸^,⁹
Other organ systems involved	Depends on type Adult often present only with rhabdomyolysis Other symptoms may include encephalopathy, cardiomyopathy, peripheral neuropathy or hypoketotic hypoglycemia⁸^,⁹	Depends on type May have hepatomegaly and history of hypoglycemia; some types have cardiac involvement⁸^,⁹	Other organ systems frequently involved, with cardiac, endocrine and central nervous systemic involvement common⁸^,⁹
Investigations leading to diagnosis	Acylcarnitine profile will suggest diagnosis, which can be confirmed by mutation analysis or fibroblast culture to assess specific enzymes in fatty acid β-oxidation pathway⁸^,⁹	Diagnosis often found on muscle biopsy showing increased glycogen stores; subtyping of the type of glycogen storage disease may require further enzyme or DNA analysis⁸^,⁹	Muscle biopsy with analysis for defects in mitochondrial DNA or nuclear DNA⁸^,⁹

MCAD = medium-chain acyl-coenzyme A dehydrogenase.

Second-wind phenomenon: improvement in exercise tolerance 10–30 minutes into exercise as muscle metabolism switches from using carbohydrates as a source of energy to using fat.