A 10-day-old female neonate undergoes newborn screening which shows elevated 17-hydroxyprogesterone (17-OHP). She has ambiguous genitalia with clitoromegaly and posterior labial fusion. Electrolytes show Na 128 mEq/L, K 6.2 mEq/L. The enzyme deficiency most likely responsible and the reason for salt-wasting is:
- A 11-beta hydroxylase deficiency; hypertension due to excess 11-deoxycortisol
- B 21-hydroxylase deficiency; lack of aldosterone and cortisol with excess androgens ✓
- C 3-beta hydroxysteroid dehydrogenase deficiency; excess weak androgens
- D 17-alpha hydroxylase deficiency; sexual infantilism with hypertension
Explanation
Classic congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency (CYP21A2 mutation) accounts for >90% of CAH cases. The enzyme block prevents conversion of 17-OHP to 11-deoxycortisol and progesterone to deoxycorticosterone, causing deficiency of both cortisol and aldosterone (salt-wasting) and accumulation of 17-OHP, which is shunted to androgen synthesis, causing virilization. Salt-wasting manifests as hyponatremia, hyperkalemia, and potential adrenal crisis. 11-beta hydroxylase deficiency causes virilization but hypertension (excess mineralocorticoids). 17-alpha hydroxylase deficiency causes hypogonadism and hypertension.
Reference: Ghai Essential Pediatrics, 10th ed.
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Written and medically reviewed by the StethoPrep medical team.