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Congenital adrenal hyperplasia — MRCPCH FOP MCQ

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HardEndocrinology and growthCongenital adrenal hyperplasiaMRCPCH FOP

A 12-day-old baby has poor feeding, vomiting and weight loss. Sodium is 124 mmol/L, potassium 6.8 mmol/L, glucose 2.4 mmol/L and examination shows clitoromegaly. What is the most likely cause?

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Correct answer: A — 21-hydroxylase deficiency causing salt-wasting congenital adrenal hyperplasia

Salt-wasting with hyperkalaemia, hypoglycaemia and virilised genitalia suggests classic congenital adrenal hyperplasia due to 21-hydroxylase deficiency. Pyloric stenosis causes hypochloraemic alkalosis rather than hyperkalaemic hyponatraemia. Neonatal withdrawal does not explain the electrolyte pattern. The pearl is that adrenal crisis is time-critical and needs hydrocortisone and fluid resuscitation.

Reference: BSPED adrenal insufficiency guidance; BNFc hydrocortisone