CYP21A2 and classic congenital adrenal hyperplasia due to 21-hydroxylase deficiency: 21-hydroxylase deficiency (21OHD) due to CYP21A2 mutation is the most common cause of CAH accounting for 95–99% of all cases (3–5), followed by 11β-hydroxylase deficiency, 17α-hydroxylase/17,20-lyase deficiency, 3β-hydroxysteroid dehydrogenase type 2 deficiency, P450 oxidoreductase deficiency, lipoid adrenal hyperplasia, and cholesterol side chain cleavage enzyme deficiency (4, 6–8).