What are the genetic changes related to cytochrome P450 oxidoreductase deficiency ?
Cytochrome P450 oxidoreductase deficiency is caused by mutations in the POR gene. This gene provides instructions for making the enzyme cytochrome P450 oxidoreductase, which plays a critical role in the formation of steroid hormones. This group of hormones includes testosterone and estrogen, which are essential for normal sexual development and reproduction; corticosteroids, which are involved in the body's response to stress; and aldosterone, which helps regulate the body's salt and water balance.  Mutations in the POR gene reduce the activity of cytochrome P450 oxidoreductase, which disrupts the production of steroid hormones. Changes in sex hormones such as testosterone and estrogen lead to problems with sexual development before birth and at puberty. In a woman who is pregnant with an affected fetus, abnormal levels of sex hormones in the fetus may cause her to have mild, temporary signs and symptoms of cytochrome P450 oxidoreductase deficiency.  Cytochrome P450 oxidoreductase is also needed for the production of cholesterol. This substance has many essential functions both before and after birth, including roles in the production of steroid hormones and in the formation and growth of bones. Mutations in the POR gene can disrupt the production of cholesterol, which likely impairs normal bone formation in the severe form of cytochrome P450 oxidoreductase deficiency. Studies suggest that a molecule called retinoic acid also plays a role in the skeletal abnormalities found in severe cases. The breakdown of retinoic acid requires cytochrome P450 oxidoreductase; if a shortage of cytochrome P450 oxidoreductase prevents retinoic acid from being broken down, the resulting excess of that molecule can stimulate the abnormal growth and fusion of bones.  The skeletal abnormalities found in the severe form of this disorder can also result from mutations in another gene, FGFR2. Some researchers use the name Antley-Bixler syndrome to describe these features, whether they are caused by mutations in the POR gene or in the FGFR2 gene. Others use the name Antley-Bixler syndrome with genital anomalies and disordered steroidogenesis for cases caused by POR gene mutations, reserving the name Antley-Bixler syndrome for cases caused by FGFR2 gene mutations.