Carnitine Shuttle & Beta-Oxidation | USMLE Step 1
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A 3-year-old boy is evaluated for poor exercise tolerance and muscle weakness. Echocardiography shows a dilated cardiomyopathy. During a recent febrile illness, he developed hypoglycemia with very little ketone production. Plasma free and total carnitine concentrations remain markedly low after recovery, and urinary testing shows excessive carnitine loss despite the low plasma concentration. He eats a varied diet, takes no medications, and has no other evidence of proximal tubular dysfunction.