Antley-Bixler syndrome is typically characterized by structural changes of the skull, bones of the face and other skeletal abnormalities. In most affected infants, there is premature closure of the joints (sutures) between different portions of the skull (craniosynostosis) Additional Craniofacial abnormalities may include a large, Prominent forehead (frontal bossing), underdeveloped middle regions of the face (midfacial hypoplasia); a large nose with a low nasal bridge; Protruding eyes (proptosis); and low-set, malformed (dysplastic) ears.
Antley-Bixler syndrome is also characterized by other distinctive skeletal changes. These may include fusion of bones of the arms that are next to each other (adjacent), particularly the forearm bone on the thumb side of the arm (radius) and the long bone of the upper arm (radiohumeral synostosis). In addition, there can be permanent flexion or extension of certain joints in a fixed position (joint contractures), leading to limited movements of the fingers, wrists, ankles, knees, and/or hips. Affected individuals may also have unusually long, thin fingers and toes (camptodactyly), structural changes on the bottom of the feet (“rocker-bottom” feet); or bowing and/or fractures of the thigh bones.
In some affected infants, a bony or thin layer of tissue may block the passageway between the nose and throat (choanal stenosis or atresia), leading to difficulty breathing. If this symptom is not treated promptly early in life, it may cause life-threatening respiratory problems.
Some individuals with Antley-Bixler syndrome may have additional symptoms. These may include certain structural defects of the urinary and genital organs (urogenital defects), inability to produce cholesterol from steroids (impaired steroidogenesis), developmental delay, and intellectual disability. ABS1 is the name given to the subtype that includes genital anomalies and disordered steroidogenesis. ABS1 is also a severe form of cytochrome P450 oxidoreductase deficiency. ABS2 is the name given to the subtype that does not include genital anomalies and disordered steroidogenesis.