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Congenital adrenal hyperplasia — MCCQE Part 1 MCQ

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HardNeonatal DistressCongenital adrenal hyperplasiaMCCQE Part 1

A 4-week-old infant has persistent non-bilious vomiting, failure to thrive, hyponatraemia (Na 128), hyperkalaemia (K 7.2), ambiguous genitalia (46,XX). Hyperpigmented. Most likely diagnosis?

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Correct answer: E — Congenital adrenal hyperplasia (21-hydroxylase deficiency)

Salt-wasting CAH: 46,XX with virilised genitalia + hyponatraemia + hyperkalaemia = classic 21-hydroxylase deficiency. Life-threatening adrenal crisis. Urgent: IV NaCl, IV hydrocortisone, glucose monitoring.

Reference: CPS / Endocrine Society