CYP21A2 and congenital adrenal hyperplasia: Congenital Adrenal Hyperplasia (CAH) is an inherited autosomal recessive disorder with a 21-hydroxylase deficiency (21-OHD) due to mutations in the 21-hydroxylase (CYP21A2) gene accounting for 90 percent.1 Clinical manifestations depend on the degree of cortisol and aldosterone deficiency.