Antley-Bixler syndrome

Antley-Bixler syndrome, also called trapezoidocephaly-synostosis syndrome, is a rare, very severe autosomal recessive malformation disorder.

Presentation
The syndrome is characterized by malformations and deformities affecting the majority of the skeleton, and other areas of the body. Presenting at birth, and even prenatally, symptoms include: brachycephaly (flat forehead), craniosynostosis (complete skull-joint closure) of both coronal and lambdoid sutures, facial hypoplasia (under-development); bowed ulna (forearm bone) and femur (thigh bone), synostosis of the radius (forearm bone), humerus (upper arm bone), and trapezoid (hand bone);  camptodactyly (fused interphalangeal joints in the fingers), thin ilial wings (outer pelvic plate), and renal malformations.

Other symptoms, such as cardiac malformations, proptotic exophthalmos (bulging eyes), arachnodactyly (spider-like fingers), as well as nasal, anal, and vaginal atresia (occlusion) have also been reported.

Pathophysiology


There are two distinct genetic mutations associated with the Antley-Bixler syndrome phenotype, which suggests the disorder may be heterogeneous. A missense mutation in the cytochrome p450 oxydoreductase (POR) gene results in abnormal steroidogenesis related to the genital malformations often found in Antley-Bixler, while mutations found in the FGFR2 gene have been shown to cause synostosis and other formal skeletal, poly and syndactylic abnormalities found in Antley-Bixler and similar disorders.

Antley-Bixler syndrome is inherited in an autosomal recessive pattern, which means the defective gene is located on an autosome, and two copies of the gene - one copy inherited from each parent - are required to be born with the disorder. The parents of an individual with an autosomal recessive disorder both carry one copy of the defective gene, but are usually not affected by the disorder.

Eponym
Antley-Bixler syndrome is named after Drs. Ray M. Antley and David Bixler, who first described the disorder in a journal report from 1975.