Exertional rhabdomyolysis as a clinical manifestation of fatty acid oxidation metabolism defect

Abstract

Background: Metabolic myopathy, an uncommon cause of rhabdomyolysis, is a rare condition which develops when there is a mismatch between energy supply and demand in muscle cells due to an underlying defect in glucose, glycogen, lipid or nucleoside metabolism1. The heterogenous group of genetic disorders that result from defects in fatty acid oxidation includes very long-chain acyl-CoA dehydrogenase (VLCAD) deficiency. Individuals with an adult onset defect in fatty acid oxidation typically present with exercise or illness induced rhabdomyolysis but may present with weakness and fatigue2. The general approach to these patients encompasses prolonged fasting avoidance, a high complex carbohydrate, low fat diet with medium chain triglyceride (MCTs) and, if needed, essential fatty acid supplementation3. Case Report: A 42-year-old female presented with one-day history of severe myalgia and dark urine after prolonged hiking. This was on a background history of myalgias post physical exertion since childhood and one past episode of atraumatic rhabdomyolysis after extreme dieting and clomiphene use. Family history revealed a brother who reported a similar muscle disorder. On presentation, laboratory evaluation showed marked elevation of plasma crea-tine kinase (85,400). Subsequent acylcarnitine profile by tandem mass spec-trometry demonstrated an abnormal pattern consistent with VLCAD deficiency. The patient was advised to have regular glucose intake frequently with exertion, not to miss meals and to keep well hydrated. She was then referred to the Adult Metabolic Service and was placed on MCTs-rich diet. Conclusion: Fatty acid oxidation metabolism defect should be considered as a possible aetiology of exertional rhabdomyolysis in an appropriate clinical setting. Metabolic disorders are often underdiagnosed, and increased awareness can lead to early diagnosis and significant improvement in outcomes.L6328011342020-09-15 <br />