An Overview of Cleidocranial Dysplasia

Cleidocranial dysplasia is a birth defect that affects the bones and teeth

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Affecting the development of bones and teeth, cleidocranial dysplasia is a birth defect that usually leads to underdeveloped or absent collar bones. As a result, those with the condition have sloped and narrow shoulders that can be brought unusually close together. This condition can also lead to a delayed or incomplete skull formation, as well as a range of other physical effects seen in the hands, feet, legs, and face. It’s very rare and occurs in approximately one in a million people worldwide.

Symptoms

There’s a great deal of variation when it comes to the severity of the effects of cleidocranial dysplasia. In a majority of cases—between 80 and 99 percent—the following are seen:

  • Underdevelopment or Absence of Clavicles: The most prominent sign is the underdevelopment or complete absence of the collar bones. These allow those with the condition to move the shoulders—which are narrower and sloped—unusually close together in front of the body.
  • Delayed Formation of Skull: While all people are born with skulls that are not fully-formed, those with this condition see delayed development. This means the sutures (junctures) between parts of the skull are slower to join, and there are larger fontanelles (the gaps between bones in seen in infants that eventually close).
  • Shorter Stature: Compared to family members, this population is comparatively shorter in height.
  • Short Shoulder Blades: The shoulder blades (scapulae) are typically shorter among those with cleidocranial dysplasia, affecting the shape of this part of the body. 
  • Dental Abnormalities: These include abnormal dental enamel and teeth prone to cavities. In addition, some may experience the growth of extra teeth or delayed formation of teeth. 
  • Wormian Bones: These are small, extra bones that appear in the skull sutures of those with this condition.
  • High, Narrow Palate: The palate is the upper portion of the mouth, and, in this population it’s higher and narrower than normal.

Oftentimes, those with cleidocranial dysplasia also have facial abnormalities, including: 

  • Wide, Short Skull: A prominent feature is a wider and shorter skull shape, which is called “brachycephaly.”
  • Prominent Forehead: Those with this condition are described as having a larger, more prominent forehead.
  • Wide-Set Eyes: Another common attribute of cleidocranial dysplasia is a wider set of the eyes, called “hypertelorism.”
  • Larger Lower Jaw: A feature that’s often present is an enlarged lower jaw, a condition called “mandibular prognathia.”
  • Other Features: A broader, flat nose, as well as a small upper-jaw are also associated with the condition.

Furthermore, in five to 79 percent of cases, there are other effects:

  • Shorter Fingers and Toes: Those with cleidocranial dysplasia often have abnormally shorter fingers and toes, a condition called brachydactyly. Fingertips are also tapered.
  • Short Thumbs: Oftentimes, the thumbs of those with this condition are broad and shorter relative to the rest of the hand.
  • Impaired Hearing: A significant amount of those with this condition suffer affected hearing acuity.
  • Osteoporosis: Many that have this condition develop osteoporosis, which is lower bone density. This causes them to be brittle and prone to fracture.
  • Spina Bifida: This is a birth defect characterized by a spinal deformity, in which the vertebrae do not form correctly around the spinal cord. 
  • Chronic Ear Infections: A higher rate of ear infections is also seen in some cleidocranial dysplasia.
  • Upper Airway Obstruction: This genetic disease can cause breathing and other respiratory problems. It can also lead to sleep apnea (snoring).
  • Knock Knees: This condition, also known as “genu valgum,” is characterized by a misalignment in the legs, leading to knees being closer together.
  • Scoliosis: Cleidocranial dysplasia is also known to cause scoliosis, which is a lateral curvature of the spine.

Causes

Cleidocranial dysplasia is a congenital birth defect caused by mutations to the RUNX2 gene. This gene regulates the development and activity of bones, cartilage, and teeth. In the earliest stages of the body’s development, cartilage—a tough but malleable tissue—makes up a large portion of the skeleton. Through a process called “ossification,” much of this cartilage turns into bones, and it’s believed that RUNX2 serves as a kind of master switch in this process.

How does it work? The mutations that affect this gene limit its ability to produce necessary proteins that spur bone and teeth growth. The RUNX2 gene is a transcription factor, meaning it attaches to certain parts of DNA to regulate activity. In cleidocranial dysplasia cases, this gene has reduced functionality—one copy per cell has reduced or no activity—hindering that skeletal, dental, or cartilage development. Notably, in approximately 30 percent cases, this mutation is not seen and the causes are unknown.

An inheritable disorder, cleidocranial dysplasia follows an autosomal dominant inheritance pattern, with just one copy of the mutated gene needed to cause the disease. This means that just one parent with the mutation will lead to it. That said, the mutation can also occur spontaneously. 

Diagnosis

When it comes to diagnosis, two primary approaches work together: physical assessment and genetic testing. Doctors (usually pediatricians) initially identify cleidocranial dysplasia through an assessment of outward signs and symptoms; in infants, this is typically is seen as enlarged fontanelles. Radiographic imaging can further confirm the absence of bone structures and other irregularities as noted above.

Once this condition is suspected, genetic testing is required to see if there truly is a disruption of the RUNX2 gene. This is done through evaluation of a tissue sample of the suspected patient, and there are several kinds of tests, each increasing in scope respectively: single-gene testing, karyotype, and a multigene panel.    

Treatment

There is no outright cure for this condition, so treatment involves progressive management of symptoms. Approaches can be broken down based on the location of symptoms:

  • For Head & Facial Issues: While it may take longer than typical for infants, the fontanelles in the skull usually close. Those with the condition may need to wear a helmet during this process. Some with the condition weigh the option of surgical correction of other abnormal facial features.
  • Skeletal Symptoms: Since reduced bone density is a common feature, those with the condition may need to take vitamin D or calcium supplements.
  • Dental Problems: Delayed development of teeth or the presence of extra teeth may require dental surgeries to correct the problem. The main goal of such work is to normalize dentition (chewing ability) in the individual with cleidocranial dysplasia.
  • Speech Therapy: Speech-language pathologists may be needed to work on speech ability in these patients.
  • Airway Obstruction: Sleep study may be indicated in cases of breathing abnormality and sleep apnea related to the condition. In these cases, treatment can include surgery.
  • Sinus & Ear Infection: In cases where there are persistent infections in the sinus cavity and ear canal, treatment needs to be proactive. In cases of persistent infection, a special tube—called a tympanostomy tube—may be necessary.

Coping

Conditions like cleidocranial dysplasia certainly present a major challenge not only to the person affected, but also to their family. Depending on the severity of the condition and alongside treatment, accommodations will need to be made to make life easier. The fallout can also be psychological. Notably, however, help is there: individual or group counseling is available for those with physical disability and their family members. Not only that, online groups and message boards can also add a sense of community for those affected.

Galen Matarazzo, one of the young stars of the television series "Stranger Things," has cleidocranial dysplasia. He raises awareness of the condition and fundraises for a charity, CCD Smiles, that funds oral surgery for others with the condition. The show creators wrote his condition into his character (Dustin) after he was cast. He began his career as a Broadway stage actor at age 9 and has been awarded the Screen Actors Guild Award for an ensemble cast.

A Word From Verywell

As tough as cleidocranial dysplasia is on both the person experiencing it and their family, it’s important to remember that our understanding of this rare condition is growing by the day. As research continues, better and more effective management approaches will continue to emerge. Furthermore, potential therapies aiming to reverse some of the effects of this condition are on the horizon. As the medical field learns more about cleidocranial dysplasia, there’s no doubt that outcomes will continue to improve. 

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Article Sources

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial policy to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. Genetic and Rare Diseases Information Center (GARD). Cleidocranial dysplasia. Published 2016. 


  3. Machol K, Mendoza-Londono R, Lee B. Cleidocranial Dysplasia Spectrum Disorder. Published 2017.


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