<unk>  (CCD), also called<unk>  dysplasia, is a birth defect that mostly affects the bones and teeth. The collarbones are typically either poorly developed or absent, which allows the shoulders to be brought close together. The front of the skull often does not close until later, and those affected are often shorter than average. Other symptoms may include a prominent forehead, wide set eyes, abnormal teeth, and a flat nose. Symptoms vary among people; however, intelligence is typically unaffected. The condition is either inherited from a person's parents or occurs as a new mutation. It is inherited in an autosomal dominant manner. It is due to a defect in the RUNX2 gene which is involved in bone formation. Diagnosis is suspected based on symptoms and X-rays with confirmation by genetic testing. Other conditions that can produce similar symptoms include mandibuloacral dysplasia, pyknodysostosis, osteogenesis imperfecta, and Hajdu-Cheney syndrome. Treatment includes supportive measures such as a device to protect the skull and dental care. Surgery may be performed to fix certain bone abnormalities. Life expectancy is generally normal. It affects about one per million people. Males and females are equally commonly affected. Modern descriptions of the condition date to at least 1896. The term is from cleido meaning collarbone, cranial from the Greek κρανιὀς meaning skull, and dysostosis meaning formation of abnormal bone.
Cleidocranial dysostosis
Osteogenesis imperfecta
Acrofrontofacionasal dysostosis
Pycnodysostosis
Nager acrofacial dysostosis
Hajdu–Cheney syndrome
Ghosal hematodiaphyseal dysplasia
Mandibuloacral dysplasia