In 2004, Fluck et al. reported that this new CAH disease was caused by a mutation in the POR gene, and they also showed that the mutation of POR could lead to a decrease in the activity of P450 enzymes including CYP21A2, CYP17A1 and CYP19A1 [6]. Here, CYP19A1 is linked to congenital adrenal hyperplasia.