Antley-Bixler syndrome is a very rare disorder characterised by craniosynostosis with midface hypoplasia, radiohumeral synostosis, femoral bowing and joint contractures. It has been described in more than 30 patients. Children present with characteristic facial features, including a large domed forehead, flat nose, and midface hypoplasia with proptosis and dysplastic ears. Arachnodactyly and/or camptodactyly have also been reported. A diverse range of malformations (cardiac, anal or vertebral) are often associated. Urogenital anomalies with sexual ambiguity due to impaired steroidogenesis can occur. Intellectual development is variable. The syndrome is genetically heterogeneous. Two genetically distinct forms are observed: type 1 Antley-Bixler syndrome is associated with heterozygous mutations in the FGFR2 gene (10q26) without impairment of steroidogenesis, whereas type 2 Antley-Bixler is associated with homozygous mutations in the POR gene (7q11.2), encoding cytochrome P450 oxidoreductase (POR), which plays a direct role in steroidogenesis. Type 2 Antley-Bixler can thus be accompanied by sexual ambiguity, but this is not a compulsory finding. Transmission is autosomal recessive. A similar clinical picture is observed in patients exposed in utero to fluconazole, a lanosterol 14 alpha-demethylase inhibitor. Treatment is symptomatic, and includes early neurosurgical as well as pulmonary management. The prognosis is poor with the majority of reported patients dying during infancy due to respiratory complications.
Last update: January 2007