A newborn develops vomiting, dehydration, and hyponatremia with hyperkalemia in the first week of life. Genitalia show clitoromegaly with fused labioscrotal folds. Serum 17-hydroxyprogesterone is markedly elevated. The deficient enzyme and the accumulated steroid precursors are:

• A 11-beta hydroxylase, with accumulation of 11-deoxycortisol and deoxycorticosterone
• B 17-alpha hydroxylase, with accumulation of mineralocorticoids and hypertension
• C 21-hydroxylase, with accumulation of 17-hydroxyprogesterone and progesterone ✓
• D 3-beta hydroxysteroid dehydrogenase, with accumulation of pregnenolone

Explanation

Classic salt-wasting congenital adrenal hyperplasia results from 21-hydroxylase deficiency, which blocks cortisol and aldosterone synthesis and shunts precursors into the androgen pathway, producing virilization in female infants. Markedly elevated 17-hydroxyprogesterone is diagnostic. 11-beta hydroxylase deficiency accumulates deoxycorticosterone and causes hypertension rather than salt wasting, while 17-alpha hydroxylase deficiency causes sexual infantilism with hypertension and low androgens.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.