Which single enzyme deficiency accounts for more than 90% of all cases of congenital adrenal hyperplasia?

• A 11-beta hydroxylase
• B 17-alpha hydroxylase
• C 21-hydroxylase ✓
• D StAR protein defect

Explanation

21-hydroxylase deficiency causes over 90% of congenital adrenal hyperplasia cases and is inherited as an autosomal recessive trait linked to the HLA complex on chromosome 6. The CYP21A2 gene lies adjacent to a highly homologous pseudogene, explaining frequent gene conversions. 11-beta hydroxylase deficiency accounts for roughly 5 to 8% of cases, while 17-alpha hydroxylase deficiency and StAR defects are rare causes.

Reference: Nelson Textbook of Pediatrics, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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