A term neonate with ambiguous genitalia is found to have blood pressure in the 95th percentile, serum sodium of 134 mEq/L, and potassium of 3.0 mEq/L. Plasma renin activity is undetectable. Which enzymatic defect explains this combination?

• A 11-beta-hydroxylase deficiency causing deoxycorticosterone accumulation ✓
• B 21-hydroxylase deficiency causing aldosterone and cortisol loss
• C 3-beta-hydroxysteroid dehydrogenase deficiency causing weak androgen production
• D 5-alpha-reductase deficiency impairing testosterone activation

Explanation

11-beta-hydroxylase blocks the final step of cortisol synthesis, diverting precursors into androgen pathways (virilization) and accumulating 11-deoxycorticosterone, a potent mineralocorticoid that causes hypertension, hypokalemia, and suppressed renin. In contrast, 21-hydroxylase deficiency produces salt wasting with hypotension and hyperkalemia, the mirror image of this picture. 3-beta-HSD deficiency under-virilizes males, and 5-alpha-reductase defect spares adrenal steroidogenesis entirely.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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