A 5-day-old neonate born of consanguineous parents presents with ambiguous genitalia in a 46,XX infant. Electrolytes show sodium 118 mEq/L and potassium 7.2 mEq/L. Serum 17-hydroxyprogesterone is markedly elevated at 50,000 ng/dL. Which enzyme deficiency is MOST likely, and which is the MOST dangerous immediate complication without treatment?

• A 11-beta-hydroxylase deficiency; hypertensive crisis
• B 3-beta-hydroxysteroid dehydrogenase deficiency; neonatal seizures
• C 17-alpha-hydroxylase deficiency; hypertension with alkalosis
• D 21-alpha-hydroxylase deficiency; adrenal crisis with severe hyponatremia ✓

Explanation

The salt-wasting form of 21-hydroxylase deficiency (the most common form of CAH, >90%) presents in 46,XX infants with virilized genitalia and potentially life-threatening salt-wasting crisis in the first 2–3 weeks. The block at 21-hydroxylase prevents cortisol and aldosterone synthesis while shunting precursors to androgens; the severe mineralocorticoid deficiency causes hyponatremia, hyperkalemia, metabolic acidosis, and cardiovascular collapse. Emergency treatment includes IV normal saline, IV hydrocortisone, and fludrocortisone supplementation.

Reference: Ghai Essential Pediatrics, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.