CYP21A2 and congenital adrenal hyperplasia: Congenital adrenal hyperplasia (CAH) is an autosomal recessive disorder of adrenal steroid biosynthesis most commonly caused by mutations or deletions in the CYP21A2 gene.1 This leads to a variable deficiency of the enzyme 21-hydroxylase (P450c21) leading to a range of manifestations [salt-wasting type (SW CAH), simple virilizing type (SV CAH), nonclassic type (NC CAH)].