A birth defect comprising a characteristic group of deformities that involve an abnormal fusion, or joining, between some of the bones of the skull and face. The fusion does not allow the craniofacial bones (bones of the skull and face) to grow normally, which affects the shape of the head and the appearance of the face as well as the positioning of the teeth. Sometimes called Apert-Crouzon syndrome, or Crouzon disease, after the doctor who first observed the birth defect, craniofacial dysostosis is caused by an abnormality abnormality in the genes. If neither parent shows signs of the syndrome, the abnormality may be the result of a change in the genetic material at the time of conception; the exact cause of this change is not known.