Cleidocranial dysplasia is a rare genetic skeletal disorder, estimated to occur in roughly one in a million births, caused by mutations in a single gene called RUNX2 that controls how bone-forming cells develop.1PubMed Central. Cleidocranial Dysplasia: A Clinico-radiographic Spectrum with Differential Diagnosis The condition gets its name from its two most recognizable features: abnormal clavicles (cleido-) and skull changes (-cranial), though its effects reach well beyond those two areas. People with cleidocranial dysplasia can have underdeveloped or completely absent collarbones, persistently open soft spots on the skull, dozens of extra teeth that never erupt, reduced bone density, and short stature, with the severity varying enormously from person to person.
What the Condition Looks Like
The hallmark most people associate with cleidocranial dysplasia is the clavicle abnormality. The collarbones can be partially formed, severely underdeveloped on one or both sides, or missing entirely. One well-documented case showed complete absence of the right clavicle with a small, underdeveloped left clavicle.2PubMed Central. Cleidocranial dysplasia with hypermobile Ehlers-Danlos syndrome: A case report When the collarbones are significantly reduced or absent, people can often bring their shoulders forward until they nearly touch in front of the chest, a striking physical finding that sometimes appears in medical textbooks as the classic demonstration of the disorder.
The skull is affected just as reliably. The anterior fontanelle, the soft spot at the top of a baby’s head that normally closes by about 18 months, can remain open well into adulthood. Skull sutures may stay unfused, and extra small irregular bones called Wormian bones often fill the gaps.3PubMed Central. Cleidocranial dysplasia with hearing loss The delayed closure of the anterior fontanelle and the midline metopic suture produces a characteristic prominent forehead known as frontal bossing.4PubMed Central. Cleidocranial dysplasia: a case report The face tends to look relatively small compared to the skull, and wide-set eyes are common.
Below the neck, the pelvis often shows a widened pubic symphysis, and the hip joints can develop coxa vara, where the angle of the thighbone is steeper than normal. Short stature affects a meaningful fraction of those with the condition, and a wide range of other skeletal changes can appear, including abnormalities in the hands and feet like underdeveloped fingertips.5PubMed Central. Cleidocranial dysplasia: a case report
The Dental Problem
For many people living with cleidocranial dysplasia, the teeth cause more day-to-day trouble than the bones. The dental picture involves two overlapping problems: too many teeth form, and the teeth that do form often refuse to come in on their own. Primary (baby) teeth may not shed normally, and permanent teeth can sit trapped in the jawbone for years or indefinitely. On top of that, the body produces extra teeth, called supernumerary teeth, that crowd the jaw and block the path of the permanent teeth that should be erupting.6PubMed. Tooth formation and eruption – lessons learnt from cleidocranial dysplasia One case report documented 26 unerupted teeth in the upper jaw and 15 in the lower jaw, with cysts forming around several of them.7PubMed Central. Cleidocranial dysplasia with hypermobile Ehlers-Danlos syndrome: A case report
Treatment for the dental issues tends to be long, staged, and demanding. The general approach involves surgically removing the supernumerary teeth, exposing the buried permanent teeth, and then using orthodontic appliances to slowly pull those teeth into position. A treatment protocol developed at UCSF has guided many cases, though outcomes depend heavily on the patient’s oral hygiene and long-term compliance with retention.8PubMed Central. Orthodontic and surgical management of cleidocranial dysplasia Newer appliance designs have shown promising results for pulling multiple impacted teeth at once, achieving functional bites with no root resorption or bone loss in reported cases.9Taiwanese Journal of Orthodontics. Orthodontic and Surgical Treatment of a Patient with Cleidocranial Dysplasia Syndrome: Introducing a New Appliance for Traction of Multiple Impacted Teeth One three-year follow-up documented stable results after orthodontic traction of 11 permanent teeth, with good occlusion, healthy gum tissue, and a balanced facial profile maintained throughout the observation period.10PubMed. Orthodontic traction in a patient with cleidocranial dysplasia: 3 years of follow-up
These treatment timelines can stretch across a decade or more when staged surgeries begin in childhood and continue through adolescence. That reality matters for quality of life. A study of 61 people with cleidocranial dysplasia found that specific bite problems significantly affected different dimensions of well-being: posterior crossbites were linked to more physical pain, anterior open bites to greater handicap, and anterior crossbites to worse functional limitation. Those who had received prosthetic dental work (dentures or implant-supported restorations) reported worse quality of life overall, likely reflecting the severity of their original dental involvement rather than the treatment itself.11PubMed Central. Oral health-related quality of life in patients with cleidocranial dysplasia: Impact of malocclusion traits and treatment modality
How RUNX2 Controls Bone Development
RUNX2 is a gene that produces a protein acting as a master switch for the cells that build bone. Without it, the precursor cells that are supposed to become osteoblasts, the bone-forming cells, never fully mature. In mice engineered to completely lack RUNX2, no bone forms at all. Mice with one working copy and one defective copy develop abnormalities strikingly similar to what you see in people with cleidocranial dysplasia: underdeveloped collarbones, open skull sutures, and fewer active osteoblasts.12Annals of Clinical & Laboratory Science. A Novel Mutation of Gene CBFA1/RUNX2 in Cleidocranial Dysplasia
The clavicle and the skull vault are particularly sensitive because they form through a process called intramembranous ossification, where bone develops directly from a sheet of connective tissue without a cartilage intermediate. This process is especially dependent on having enough functional RUNX2. But the clavicle also partly forms through endochondral ossification, which goes through a cartilage stage first, meaning RUNX2 disruption hits it from both directions. The short stature seen in some people with cleidocranial dysplasia provides further evidence that endochondral bone growth, the process responsible for long bone elongation, is affected too.13Annals of Clinical & Laboratory Science. A Novel Mutation of Gene CBFA1/RUNX2 in Cleidocranial Dysplasia
A mouse study that allowed researchers to dial RUNX2 activity to specific levels revealed a surprisingly narrow threshold. Mice producing about 55 to 70 percent of the normal amount of RUNX2 protein developed clavicle and skull defects consistent with cleidocranial dysplasia, while mice producing 79 to 84 percent had completely normal skeletons.14Human Molecular Genetics. A Runx2 threshold for the cleidocranial dysplasia phenotype The implication is that bone development works on a knife’s edge of RUNX2 activity. A modest shortfall can tip the system into disease, and the spectrum of severity in patients probably reflects how much functional RUNX2 a given mutation leaves intact.
Why Severity Varies So Much Between People
One of the more frustrating aspects of cleidocranial dysplasia for both patients and clinicians is that two people in the same family, carrying the exact same mutation, can look quite different. One might have barely noticeable clavicle underdevelopment and manageable dental issues, while a sibling has absent collarbones, dozens of impacted teeth, and significant short stature. The condition follows autosomal dominant inheritance, meaning you only need one defective copy of RUNX2 to develop it. About a third of cases arise as new spontaneous mutations in people with no family history.15PubMed. Cleidocranial dysplasia: Clinical, endocrinologic and molecular findings in 15 patients from 11 families
The type and location of the mutation within the RUNX2 gene does influence the clinical picture, at least statistically. A systematic review found that missense mutations within the functionally critical runt homology domain (RHD) of the protein were significantly associated with supernumerary teeth, large head size, delayed fontanelle closure, limited shoulder movement, pubic symphysis abnormalities, and underdeveloped hip bones, compared to other types of mutations.16PubMed Central. The impact of RUNX2 gene variants on cleidocranial dysplasia phenotype: a systematic review Small insertions and deletions that did not shift the reading frame were associated with fewer features overall. A study of 11 patients found a pattern where families with severe dental involvement tended to carry missense mutations that directly impaired the runt domain, while families with milder dental findings either had no detectable RUNX2 mutation or had mutations outside that critical region.17PubMed Central. Cleidocranial dysplasia: oral features and genetic analysis of 11 patients
On the craniofacial side, truncating mutations (those that produce a shortened, usually nonfunctional protein) were associated with a shorter skull base and more pronounced jaw discrepancies compared to non-truncating variants, though interestingly no significant link was found between mutation type and the number or distribution of extra teeth in that particular analysis.18PubMed Central. Correlation of RUNX2 Variants With Craniofacial-Dental Phenotypes in Cleidocranial Dysplasia This uneven picture, where genotype clearly predicts some features but not others, underscores that other genetic and developmental factors also shape the final outcome.
Bone Density and Osteoporosis Risk
Because RUNX2 is essential for osteoblast maturation, it should not be surprising that bone density is often compromised. Yet this aspect of cleidocranial dysplasia has historically received less attention than the more visible skeletal and dental features. A study of 15 patients from 11 families found osteoporosis in about 57 percent and osteopenia (a milder reduction in bone density) in about 21 percent.19PubMed. Cleidocranial dysplasia: Clinical, endocrinologic and molecular findings in 15 patients from 11 families Earlier family studies also flagged markedly reduced bone density in affected members, suggesting that osteoporosis risk in cleidocranial dysplasia has been underemphasized.20PubMed. Identification of novel CBFA1/RUNX2 mutations causing cleidocranial dysplasia
Some cases have also shown biochemical findings resembling hypophosphatasia, a different metabolic bone disorder, including low alkaline phosphatase activity and increased urinary phosphoethanolamine, even though the underlying cause was a RUNX2 mutation rather than anything wrong with the alkaline phosphatase gene itself. Researchers have suggested these metabolic changes are secondary effects of disrupted early bone maturation.21PubMed. Cleidocranial dysplasia with decreased bone density and biochemical findings of hypophosphatasia For adults with cleidocranial dysplasia, this means bone density monitoring and fracture prevention deserve more routine attention than they have traditionally received.
Complications Beyond the Bones and Teeth
A natural history study that tracked a broader range of health outcomes in people with cleidocranial dysplasia identified several complications at higher rates than previously recognized. These included knock-knees, scoliosis, flat feet, recurrent sinus infections, upper airway complications, repeated middle ear infections, and hearing loss.22PubMed. A natural history of cleidocranial dysplasia The hearing loss can be conductive (related to the structural problems in the middle ear and temporal bone) or mixed. Recurrent ear infections in children with the condition may partly stem from abnormal skull-base anatomy that affects how the eustachian tubes drain.
Scoliosis, when present, occasionally requires active treatment. Case reports describe the use of growing-rod systems in young patients with early-onset spinal curvature, followed by definitive spinal fusion once growth is complete, with successful outcomes and no complications at medium and long-term follow-up.23PubMed Central. The Treatment of Cleidocranial Dysostosis (Scheuthauer-Marie-Sainton Syndrome), a Rare Form of Skeletal Dysplasia, Accompanied by Spinal Deformities: A Review of the Literature and Two Case Reports Family screening can sometimes uncover previously undiagnosed relatives. In one report, Wormian bones in the skull and defective ossification of the pubic symphysis found incidentally in a girl being evaluated for mild scoliosis led to a radiological evaluation of her family that identified additional affected members.24PubMed. Cleidocranial dysplasia. A family study.
Prenatal Diagnosis
Cleidocranial dysplasia can sometimes be detected before birth, though the ultrasound findings are subtle enough that the diagnosis is often missed, especially when there is no known family history. Absent or short clavicles on a fetal anatomy scan are the most distinctive clue, but they require the sonographer to be specifically looking at clavicle length. When abnormal ultrasound findings raise suspicion, amniocentesis and genetic sequencing of the RUNX2 gene can confirm the diagnosis. In reported cases where prenatal ultrasound suggested the condition and genetic testing followed, Sanger sequencing identified frameshift deletions in RUNX2 that were absent in both parents, confirming new mutations.25PubMed Central. Prenatal diagnosis of cleidocranial dysplasia: Case report on two cases with a negative family history
A definitive prenatal diagnosis ideally combines family history (when available), ultrasound findings, and genetic analysis.26PubMed Central. Prenatal ultrasonography and genetic analysis of fetal cleidocranial dysplasia: A case report Since roughly a third of cases are sporadic, the absence of a family history does not rule the condition out. For families with a known RUNX2 mutation, targeted genetic testing from chorionic villus sampling or amniocentesis can provide a definitive answer early in pregnancy.
Anesthetic Considerations
People with cleidocranial dysplasia face specific challenges when they need surgery, whether for dental procedures, orthopedic interventions, or unrelated reasons like pregnancy. The anatomical changes in the head, mouth, neck, and spine can make both general anesthesia and spinal or epidural anesthesia more difficult. The narrow palate, crowded teeth, and sometimes small jaw can complicate intubation. Vertebral anomalies, including unfused arches and scoliosis, can make placing a spinal or epidural needle unpredictable.27PubMed. Anesthetic management of a patient with cleidocranial dysplasia undergoing various obstetric procedures
Case reports emphasize that imaging of the spine before any planned neuraxial anesthesia and careful preparation for airway management are important.28PubMed Central. Anesthetic management during a cesarean section in a patient with cleidocranial dysplasia: a case report When possible, peripheral nerve blocks under sedation offer a way to avoid airway manipulation altogether, as demonstrated in a case involving an upper limb fracture.29The Anaesthesiologist. Anaesthetic Management of Upper Limb Fracture in a Patient With Cleidocranial Dysplasia One woman with cleidocranial dysplasia documented across four cesarean sections, one vaginal delivery, and a minor gynecological procedure required different anesthetic approaches each time, illustrating how flexibility is essential.30PubMed. Anesthetic management of a patient with cleidocranial dysplasia undergoing various obstetric procedures If you have cleidocranial dysplasia and are facing any surgical procedure, making sure your anesthesiologist is aware well in advance is more than a courtesy; it can genuinely change the plan for how you are kept safe during the operation.
Life Expectancy and Long-Term Outlook
Cleidocranial dysplasia does not typically shorten lifespan. People with the condition live into old age, and many of the skeletal abnormalities are either cosmetic or manageable with appropriate care. The open fontanelle, while it sounds alarming, is usually covered by thick fibrous tissue and does not place the brain at significant risk in everyday life, though protective headwear for contact sports is sensible. The real burden of the disease is cumulative and largely dental, orthopedic, and otologic: years of dental procedures, monitoring and sometimes treating scoliosis or low bone density, and managing recurrent ear and sinus infections.
There is no standard effective treatment that addresses the underlying genetic cause.31PubMed Central. Familial Cleidocranial Dysplasia Management is entirely symptomatic and multidisciplinary, typically involving orthodontists, oral surgeons, orthopedic specialists, ENT physicians, audiologists, and sometimes endocrinologists for bone density. Because severity varies widely, even among family members sharing the same mutation, each person’s care plan needs to be individualized. The identification of RUNX2 as the gene responsible in about 70 percent of cases has made genetic counseling more straightforward, but it also means that in roughly 30 percent of clinically diagnosed cases the underlying mutation is not found by standard sequencing of that gene.32PubMed. Cleidocranial dysplasia: Clinical, endocrinologic and molecular findings in 15 patients from 11 families
RUNX2 and the Vertebrate Skeleton
The gene at the center of cleidocranial dysplasia has a fascinating evolutionary backstory. RUNX2 is not just any bone gene; it appears to have been pivotal in the emergence of the bony skeleton across vertebrate history. The RUNX2 protein contains a glutamine-alanine (QA) repeat domain that is absent from its close relatives RUNX1 and RUNX3. Research tracing this repeat domain across vertebrate species found that its duplication and divergence from an ancestral gene roughly 450 million years ago may have helped establish a bone-specific genetic program, effectively providing the molecular foundation for the internal skeleton that defines vertebrates.33Communications Biology. Evolution and expansion of the RUNX2 QA repeat corresponds with the emergence of vertebrate complexity
Studies in frogs add another piece to the puzzle. In the African clawed frog, RUNX2 plays a role in cartilage formation that it does not seem to play in mammals, suggesting that the gene’s function shifted over evolutionary time toward an increasingly exclusive role in cartilage maturation and bone formation within the lineage that led to reptiles, birds, and mammals.34PubMed. Runx2 is essential for larval hyobranchial cartilage formation in Xenopus laevis The same gene that, when mutated, causes the open fontanelles and absent collarbones of cleidocranial dysplasia is, in an evolutionary sense, the gene that gave vertebrates their skeletons in the first place. That deep importance helps explain why even modest reductions in its activity produce such widespread effects across the body.