A 3-week-old 46,XX infant presents with ambiguous genitalia including clitoromegaly and labial fusion. Blood pressure is 110/75 mmHg (elevated for age). Serum 11-deoxycortisol is markedly elevated. Electrolytes show hypokalemia (K 2.8 mEq/L) with mild metabolic alkalosis. What is the underlying enzyme deficiency?

• A 21-hydroxylase deficiency
• B 11-beta hydroxylase deficiency ✓
• C 3-beta hydroxysteroid dehydrogenase deficiency
• D 17-alpha hydroxylase deficiency

Explanation

11-beta hydroxylase deficiency causes accumulation of 11-deoxycorticosterone, a potent mineralocorticoid, producing hypertension and hypokalemia. This contrasts with 21-hydroxylase deficiency which causes salt-wasting with hyponatremia and hyperkalemia. Both cause virilization in 46,XX infants due to shunting of precursors to the androgen pathway.

Reference: Nelson Textbook of Pediatrics, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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