Background: Carnitine is essential for transporting long-chain fatty acids into mitochondria and promotes energy metabolism via β-oxidation of long-chain fatty acids. Although carnitine is also present in the peripheral blood, 98% of total carnitine is stored in muscle tissue. Neuromuscular diseases accompanied by muscle atrophy are likely to lead to secondary carnitine deficiency, owing to the reduced amount of total carnitine stored in the body.
Case presentation: An 8-y-old Japanese boy with Fukuyama-type congenital muscular dystrophy accompanied by severe psychomotor retardation had been constantly bedridden, suffered from dysphagia, and had been fed through a gastrostomy tube since the age of 1 y. Regular oral carnitine supplementation (5 mg/kg/d of levocarnitine) was initiated at the age of 7 y, which increased serum carnitine value to within the normal range (serum total carnitine concentration, 58.5-60.9 μmol/L; acylcarnitine concentration, 45.8-55.0 μmol/L; free carnitine concentration, 5.9-12.7 μmol/L). He developed a fever, vomiting, and gastrointestinal bleeding at the age of 8 y. He fell into a coma and visited an emergency room 12 h later. Hypoglycemia and hypocarnitinemia (serum total carnitine concentration, 3.7 μmol/L; acylcarnitine concentration, 2.9 μmol/L; free carnitine concentration, 0.8 μmol/L; acyl-to-free carnitine ratio, 3.6) were observed, and he was found to be negative for urinary ketone bodies.
Conclusions: Neuromuscular diseases accompanied by muscle atrophy may lead to acute carnitine deficiency, even if the serum carnitine concentration is within the normal range before onset. During sick days, it may be necessary to modify a patient's treatment, such as increasing both oral supplementation and intravenous administration of carnitine.
Keywords: Carnitine deficiency; Fukuyama-type congenital muscular dystrophy.
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