cleidocranial dysostosis A genetic disorder of bone development that is characterized by absent or incompletely formed collarbones and cranial and facial abnormalities that may include square skull, late closure of the sutures of the skull, late closure of the fontanels, low nasal bridge, delayed eruption of the teeth, and abnormal permanent teeth. A child with this disorder can bring his or her shoulders together, or nearly so. The gene for cleidocranial dysostosis has been found on chromosome 6 in band p21. Also known as cleidocranial dysplasia and craniocleidodysostosis.