An 8-year-old girl presents with pubic hair (Tanner stage 2), axillary hair, but no breast development and no clitoromegaly. She has advanced bone age. 17-hydroxyprogesterone is markedly elevated. The most common enzyme deficiency responsible for this presentation is:

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

Explanation

21-hydroxylase deficiency (CYP21A2 mutations) accounts for >90% of congenital adrenal hyperplasia (CAH). In the simple virilising form, cortisol and aldosterone biosynthesis are impaired, causing accumulation of 17-OHP and shunting to androgens. Girls present with premature pubic/axillary hair, advanced bone age, and clitoromegaly (in classic form); markedly elevated 17-OHP is the diagnostic hallmark. 11-beta hydroxylase deficiency presents with hypertension due to accumulation of 11-deoxycortisol and 11-deoxycorticosterone. 17-alpha hydroxylase deficiency causes sex hormone deficiency.

Reference: Ghai Essential Pediatrics, 10th ed.

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Written and medically reviewed by the StethoPrep medical team.