A term newborn girl has ambiguous genitalia with clitoromegaly and fused labioscrotal folds. On day 6 she becomes lethargic with poor feeding, sodium 126 mEq/L, potassium 6.8 mEq/L, and mild dehydration. Which biochemical finding confirms the diagnosis?

• A Elevated maternal serum human chorionic gonadotropin
• B Markedly elevated 17-hydroxyprogesterone ✓
• C Low serum 11-deoxycortisol
• D Elevated plasma renin with low aldosterone and normal androgens

Explanation

Virilised female newborn with salt-wasting crisis in the first two weeks of life is classic 21-hydroxylase deficiency congenital adrenal hyperplasia. The blocked enzyme causes cortisol and aldosterone deficiency with shunting into androgen production, so 17-hydroxyprogesterone accumulates and is markedly elevated, the confirmatory test. Low aldosterone with low androgens would suggest hypoaldosteronism instead, and 11-deoxycortisol is elevated in 11-beta-hydroxylase deficiency, which causes hypertension rather than salt wasting.

Reference: Nelson Textbook of Pediatrics, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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