The congenital adrenal hyperplasia syndrome Congenital adrenal hyperplasia (CAH) is caused by autosomal recessive mutations in the CYP11B1 gene encoding steroid 11 β-hydroxylase, CYP17A1 gene encoding 17 α-hydroxylase or CYP17A2 gene encoding 21-hydroxylase (Fig. 1), resulting in androgen excess, virilization, and hypertension. The gene discussed is CYP17A1; the disease is congenital adrenal hyperplasia.