A 16-day-old girl develops vomiting, poor feeding, and dehydration. Examination shows ambiguous genitalia. Sodium is 118 mEq/L, potassium 7.4 mEq/L, and random glucose 42 mg/dL. Which single laboratory finding confirms the most likely diagnosis?

• A Elevated plasma ACTH with low androgens
• B Elevated 11-deoxycortisol
• C Low renin with low aldosterone
• D Elevated 17-hydroxyprogesterone ✓

Explanation

Salt-wasting congenital adrenal hyperplasia from 21-hydroxylase deficiency presents in the neonatal period with vomiting, hyponatraemia, hyperkalaemia, hypoglycaemia, and virilisation in girls. Accumulated steroid precursors shunt into androgen pathways, so 17-hydroxyprogesterone is markedly elevated. Elevated 11-deoxycortisol would indicate 11-beta-hydroxylase deficiency, which causes hypertension rather than salt wasting. Androgens are high, not low, because the enzymatic block diverts substrate toward the androgen pathway.

Reference: Nelson Textbook of Pediatrics, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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