Congenital adrenal hyperplasia (CAH) stems from inherited enzyme deficiencies that impair cortisol synthesis, with 21-hydroxylase deficiency accounting for 95% to 99% of cases, caused by mutations in the CYP21A2 gene [1, 2]. The gene discussed is CYP21A2; the disease is classic congenital adrenal hyperplasia due to 21-hydroxylase deficiency.