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CAH – salt-wasting — RACP Paediatrics MCQ

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ModerateEndocrineCAH – salt-wastingRACP Paediatrics

A neonate is born with ambiguous genitalia: clitoromegaly, fused labioscrotal folds, and a single perineal opening. There is progressive vomiting on day 5. Na is 120, K is 7.5, glucose 1.8 mmol/L. 17-OHP is markedly elevated. Karyotype is 46,XX. What is the most likely diagnosis?

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Correct answer: C — 46,XX CAH (21-hydroxylase deficiency)

The most common cause of ambiguous genitalia in a 46,XX neonate is congenital adrenal hyperplasia (21-hydroxylase deficiency). The salt-wasting crisis with hyponatraemia, hyperkalaemia, and hypoglycaemia plus markedly elevated 17-OHP confirms the diagnosis. This is a life-threatening emergency requiring immediate IV hydrocortisone and fluid/glucose resuscitation.

Reference: RCH Melbourne – 2023 – DSD CPG; RACP Paediatric Curriculum – Endocrine