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.