CYP21A2 and congenital adrenal hyperplasia: CAH is a common autosomal recessive disease caused by mutations in genes encoding enzymes in the adrenal steroidogenic pathway, including steroid 21-hydroxylase (CYP21A2), 11b-hydroxylase (CYP11B1), 17a-hydroxylase (CYP17A1), and 3b-hydroxysteroid dehydrogenase type 2 (HSD3B2).