Fatty-acid oxidation disorders — branching viva

Emergency department: a 14-month-old previously well girl presents with a two-day febrile illness, vomiting and progressive lethargy. She has not eaten for 14 hours. She is drowsy with a bedside glucose of 1.8 mmol/L and point-of-care ketones of 0.1 mmol/L. The examiner asks: why is this a fatty-acid oxidation disorder until proven otherwise, what is the immediate emergency protocol, how does the acylcarnitine profile localise the defect, what is the fasting-energy-failure mechanism, and what are the safe fasting intervals — then branches to a second case of a six-month-old with dilated cardiomyopathy and profoundly low plasma carnitine, and asks you to explain the OCTN2 defect and its dramatic response to high-dose carnitine.