CYP19A1 and congenital adrenal hyperplasia due to cytochrome P450 oxidoreductase deficiency: POR deficiency results from homozygous or compound heterozygous POR gene mutations, which codifies for an electron donor protein to various mitochondrial enzymes, especially CYP21A2 and CYP17A1, but also CYP19A1, CYP51A1, and CYP26A1-C1.