GeneDx :: Tests :: Cytochrome P450 Oxidoreductase Deficiency, Antley-Bixler syndrome (ABS)

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Cytochrome P450 Oxidoreductase Deficiency, Antley-Bixler syndrome (ABS)

Cytochrome P450 oxidoreductase (POR) deficiency causes steroid hormone abnormalities occur in all patients, consistent with a form of congenital adrenal hyperplasia (CAH) causing deficiencies of both 21-hydroxylase and 17α -hydroxylase/17,20-lyase. Disordered sex development has been observed in both males and females, and ambiguous genitalia is a common finding. At the severe end of the spectrum, patients may also have skeletal and craniofacial findings consistent with Antley-Bixler syndrome, including craniosynostosis, brachycephaly, severe midface hypoplasia, radiohumeral synostosis, and multiple joint contractures.

POR is the only gene known to be associated with P450 oxidoreductase deficiency; however, the sensitivity of POR sequencing is not well established at this time. An estimated 12% of patients have only one identifiable mutation in the POR gene, indicating that some mutations lie outside of the coding exons and would not be detected with current methodology. Of patients with a clinical diagnosis of Antley-Bixler syndrome, 59% have at least one mutation in the POR gene. The sensitivity of POR sequencing is highest in patients with ABS who have abnormal steroids and/or genitalia.

Analysis is performed by bi-directional sequencing of all 15 coding exons and the exon/intron splice junctions of the POR gene. Mutations found in the first person of a family to be tested are confirmed by repeat analysis using sequencing, restriction fragment analysis, or another appropriate method.

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cytochrome P450 oxidoreductase deficiency, POR deficiency, POR, Antley-Bixler syndrome, ABS, congenital adrenal hyperplasia