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MCAD deficiency — RACP Paediatrics MCQ

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HardGenetics and metabolicMCAD deficiencyRACP Paediatrics

A 14-month-old has a hypoglycaemic seizure after a prolonged fast during gastroenteritis. Ketones are absent, ammonia is mildly raised and acylcarnitine profile suggests medium-chain acyl-CoA dehydrogenase deficiency. What would you advise the parents?

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Correct answer: C — Avoid prolonged fasting and use an emergency glucose plan during illness

MCAD deficiency prevents adequate fatty acid oxidation during fasting, causing hypoketotic hypoglycaemia; families need fasting avoidance and an emergency carbohydrate/glucose plan. A ketogenic diet is dangerous because the child cannot safely use fatty acids for energy. The pearl is that absent ketones during hypoglycaemia are abnormal and suggest a fatty acid oxidation disorder or hyperinsulinism.

Reference: Australian Newborn Bloodspot Screening Programme; Metabolic specialist guidance