Congenital adrenal hyperplasia due to 21-hydroxylase deficiency in all its forms, accounts for over 95% of diagnosed cases of congenital adrenal hyperplasia, and 'CAH' in most contexts refers to 21-hydroxylase deficiency. Congenital adrenal hyperplasia due to 21-hydroxylase deficiency in all its forms, accounts for over 95% of diagnosed cases of congenital adrenal hyperplasia, and 'CAH' in most contexts refers to 21-hydroxylase deficiency.