CCD, or cleidocranial dysplasia, is a rare genetic disorder that affects how bones and teeth develop throughout the body. It occurs in roughly 1 per million people worldwide, though the true number is likely higher because mild cases often go undiagnosed. The condition is present from birth and primarily causes underdeveloped or absent collarbones, delayed closure of the skull’s soft spots, and significant dental problems including extra teeth that fail to emerge properly.
What Causes CCD
CCD is caused by a change in a gene called RUNX2, which acts as a master switch for bone-building cells. This gene tells the body how to produce a protein that drives the development and maintenance of bone tissue. When the gene is altered, the protein doesn’t function correctly, and bones throughout the body form incompletely or on a delayed timeline.
The condition follows an autosomal dominant inheritance pattern, meaning a single copy of the altered gene from one parent is enough to cause it. If one parent has CCD, each child has a 50% chance of inheriting it. However, 30% to 40% of cases arise spontaneously as new mutations in people with no family history of the disorder. The severity varies widely, even within the same family. One person might have barely noticeable symptoms while a sibling with the same mutation has significant skeletal differences.
How CCD Affects the Skeleton
The most recognizable feature of CCD is abnormal collarbones. These can range from completely absent to partially formed or broken into disconnected segments, and the outer portions tend to be more affected than the inner portions near the breastbone. People with severely underdeveloped collarbones can sometimes bring their shoulders together in front of their chest, a physical sign that often prompts the initial diagnosis.
The skull is also significantly affected. The soft spots (fontanelles) that normally close in infancy may remain open well into adulthood, and the sutures between skull bones stay wider than usual. Small extra bone fragments called Wormian bones often form within these open sutures. The sinuses in the forehead and around the nose may never fully develop, which creates a distinctive facial profile where the lower jaw appears more prominent than the upper jaw.
Beyond the skull and collarbones, CCD affects the pelvis, hands, and spine. The pubic bone is slow to harden, the hip joints may develop abnormally with shortened femoral necks, and the shoulder blades tend to be undersized. In the hands, the second finger bone is often unusually long, and the fingertips may appear shortened. Reduced bone density is common across the entire skeleton, and some people with CCD experience frequent fractures as a result. Occasional complications include scoliosis, extra ribs, a narrow upper chest, and a small pelvis.
Dental Problems Are Often the Biggest Challenge
For many people with CCD, the dental complications create more day-to-day difficulty than the skeletal ones. Baby teeth tend to hang on far longer than normal, sometimes persisting into adulthood. Permanent teeth often remain trapped in the jawbone and never erupt on their own. On top of that, the body produces extra (supernumerary) teeth that crowd the jaw and block the path of the permanent teeth trying to come in. These extra teeth appear most frequently in the lower premolar area and the upper front of the mouth.
A teenager with CCD might still have a mouth full of baby teeth with dozens of unerupted permanent and extra teeth visible on a panoramic X-ray beneath the surface. Without intervention, this leads to difficulty chewing, poor alignment, and an increased risk of cavities in the retained baby teeth. Managing these dental issues typically requires a multi-step process that begins in childhood and continues through skeletal maturity: treating cavities in the baby teeth first, then surgically removing retained baby teeth and extra teeth in stages, and using orthodontic treatment to help the permanent teeth move into position. In some cases, permanent teeth are too deeply impacted to be saved and must be removed as well, with prosthetic replacements planned later.
Hearing Loss and Sinus Problems
Because CCD affects the bones of the skull and face, it can create problems beyond the skeleton itself. The tiny bones of the middle ear may be structurally abnormal, leading to conductive hearing loss, where sound doesn’t transmit efficiently from the eardrum to the inner ear. In some cases, there is also a smaller component of nerve-related hearing loss. The temporal bone surrounding the ear can become unusually dense, and abnormal formation of the palate or the tubes connecting the throat to the middle ear can contribute to fluid buildup and further hearing difficulty. Some children with CCD need small tubes placed in their eardrums to help with drainage.
Underdeveloped sinuses and facial bones also make people with CCD more prone to recurrent sinus infections and, in some cases, pneumonia. Regular monitoring of hearing and respiratory health is an important part of long-term care.
How CCD Is Diagnosed
Doctors can often suspect CCD based on physical examination and X-rays alone. The combination of open skull sutures, abnormal collarbones, and characteristic dental findings on a panoramic X-ray is distinctive enough to point toward the diagnosis in most cases. X-rays of the pelvis, hands, and chest reveal additional hallmarks like a wide pubic joint, lengthened second finger bones, and a narrow, cone-shaped upper chest.
Genetic testing confirms the diagnosis by identifying a mutation in the RUNX2 gene. Testing usually starts with sequencing the gene to look for small changes. If that comes back normal, a second round of testing looks for larger deletions or duplications that sequencing might miss. In about 30% of clinically diagnosed cases, current testing does not find a mutation in RUNX2, which means the clinical and X-ray findings remain the primary basis for diagnosis in those individuals.
Long-Term Outlook and Management
CCD does not shorten life expectancy. People with the condition have a normal lifespan, though they typically require ongoing medical and dental care throughout childhood and into early adulthood. Height is often shorter than average but varies depending on the severity of the skeletal involvement.
Management is tailored to each person’s specific set of features. The dental treatment plan is usually the most involved, sometimes spanning a decade or more with staged surgeries and orthodontic work. If the upper jaw remains significantly underdeveloped by the time the skeleton has finished growing, surgical correction of the jaw may be recommended. Bone density is monitored, and fracture prevention becomes a consideration, particularly in those with more pronounced osteoporosis. Hearing assessments should be done regularly starting in childhood so that any loss is caught early and addressed with hearing aids or ear tubes as needed.
Because CCD varies so much in severity, some people require only minor dental work and periodic checkups, while others need complex surgical and orthodontic interventions over many years. Coordinated care between orthopedic specialists, dentists, oral surgeons, and audiologists gives the best results.