Fatty-acid oxidation disorders — formative SAQs

SAQ 1 (10 marks)

A 14-month-old girl is brought to the emergency department with a two-day history of vomiting and lethargy following a febrile illness. She has not eaten for approximately 14 hours. On arrival she is drowsy, her bedside glucose is 1.8 mmol/L, and a point-of-care ketone measurement returns 0.1 mmol/L. ^{[1] [5]}

a) Explain why the combination of a low blood glucose with inappropriately low ketones is the signature of a fatty-acid oxidation disorder, and describe the physiological mechanism that produces this pattern. (3 marks) ^{[1] [5]}

b) Outline the immediate resuscitation you perform, including the specific intravenous therapy and why glucagon would be ineffective. (3 marks) ^{[1] [2]}

c) Describe the critical sample you collect at the time of hypoglycaemia and the first-tier diagnostic test that will localise the defect. Explain how plasma acylcarnitines would distinguish MCAD deficiency from a long-chain defect. (2 marks) ^[1]

d) Discuss the long-term management plan, including fasting avoidance, the emergency sick-day plan, and how newborn screening changed the prognosis of this condition. (2 marks) ^{[5] [7]}