Antley-Bixler syndrome (ABS) is a rare congenital disorder characterized by numerous craniofacial,
skeletal and, in some cases, urogenital abnormalities resulting from disordered steroidogenesis. Known
genetic causes in sporadic cases of ABS include dominant mutations in the fibroblast growth factor 2
receptor gene (FGFR2). Recent research shows surprisingly that symptoms of Antley-Bixler syndrome,
combined with disordered steroidogenesis and urogenital anomalies, are caused by mutations in the POR
gene that encodes NADPH-cytochrome P450 oxidoreductase (CYPOR). CYPOR is a four domaincontaining
monomeric flavoprotein that contains two flavins, flavin adenine dinucleotide (FAD) and
flavin mononucleotide (FMN), a binding site for NADPH, and the N-terminal sequence of 25 amino
acids which determines the microsomal localization of the protein. CYPOR is the electron donor to
microsomally localized cytochromes P450 that participate in xenobiotic metabolism and
steroidogenesis. Mutations in the POR gene lead to apparent diminished activity of some P450 enzymes.
Association of CYPOR with ABS discloses new facts about this disease and recent research shows that
patients with ABS-like skeletal anomalies, but with mutations in the POR gene and disordered
steroidogenesis, represent a new disorder called POR deficiency.
Antley-Bixler syndrome, POR deficiency, NADPH-cytochrome P450 oxidoreductase,