Description, Causes and Risk Factors:
A developmental disorder characterized by absence or hypoplasia of clavicles, box-shaped skull with open sutures, frontal bossing, womian bones, ability to oppose shoulders, and missing teeth; autosomal dominant inheritance, caused by mutation in the transcription factor gene (CBFA1) encoding core-binding factor, runt domain, alpha-subunit 1 on 6p. There is an autosomal recessive form. The disorder is very rare and occurs in approximately 1 per million individuals Worldwide.
The etiology of Cleidocranial dysostosis is unknown. It can have dominant and recessive pattern of inheritance and 16% patients are reported to be sporadic.
Cytogenic abnormalities on chromosome 6 was suggested by Genetic genealogy. The condition has been mapped to a microdeletion of chromosome band 6p21, t(6;18) (p12; q24) translocation and pericentric inversion of chromosome 6. The most striking features of this syndrome are partial or complete absence (in about 10% of cases) of clavicles causing unusual mobility of the shoulders and late closure of fontanelles resulting in frontal bossing.
The RUNX2 gene provides instructions for making a protein that is involved in bone and cartilage development and maintenance. This protein is a transcription factor, which means it attaches (binds) to specific regions of DNA and helps control the activity of particular genes. Researchers believe that the RUNX2 protein acts as a "master switch," regulating a number of other genes involved in the development of cells that build bones (osteoblasts). Some mutations change one protein building block (amino acid) in the RUNX2 protein. Other mutations introduce a premature stop signal that results in an abnormally short protein. Occasionally, the entire gene is missing.
These genetic changes reduce or eliminate the activity of the protein produced from one copy of the RUNX2 gene in each cell, decreasing the total amount of functional RUNX2 protein. This shortage of functional RUNX2 protein interferes with normal bone and cartilage development, resulting in the signs and symptoms of cleidocranial dysostosis. In rare cases, affected individuals may experience additional, unusual symptoms resulting from the loss of other genes near RUNX2.
Patients with Cleidocranial dysostosis exhibit a high, narrow, arched palate and an actual cleft palate appears to be common. One of the outstanding oral finding is prolonged retention of the deciduous teeth and subsequent delay in eruption of the succedaneous teeth. Scientists have postulated various views regarding the etiology of non-eruption, such as lack of cellular cementum, defectiveness in post cementum formation, presence of thick connective tissue between oral epithelium and dental follicle, delayed tooth formation and maturation. Furthermore, it is characteristic for numerous uninterrupted supernumerary teeth to be found by roentgenographic examination. These are most prevalent in the mandibular, premolar, and incisor areas. The reason for the formation of multiple supernumerary teeth is still unknown.
Skeletal Class III tendency / mandibular prognathism in cleidocranial dysostosis can be attributed to its uninterfered growth due to hypoplastic maxilla and upward and forward mandibular rotation.
Treatment obviously extends over many years and clinicians should be aware of the child's compliance. Once the full permanent dentition has been brought into the mouth and into good alignment and function, follow up radiographs should be made to check for the development of new supernumerary teeth which seems to occur in the early to mid teens.
Wide nasal bridge.
Missing collar bone.
Delayed closure of fontanelle ("soft spots")
Prominent forehead (frontal bossing).
Jaw and bone that are sticks out.
Decreased bone density.
Theradiographic evaluation of patients is the most important andreliable means to confirm the diagnosis.Radiological investigations included an orthopantomogram, lateral cephalogram, anteroposterior view ofthe skull, chest radiograph, hand-wrist radiograph, anteroposterior and lateral views of the spine, anteroposteriorviews of the pelvis and both hips, and 3D computedtomography of the skull.
Genetic counseling is appropriate for prospective parents witha family history of Cleidocranial dysostosis or where one or both parents are affected.
There is no specific treatment for Cleidocranial dysostosis, as the bony abnormalities cause little problem although care of the oral condition is important. The dental problems are the most significant complications. A Multidisciplinary approach to treatment of these patients utilizing a pedodontist, an orthodontist and an oral surgeon is recommended. The retained primary teeth should be restored if they become carious since extraction does not necessarily induce eruption of the permanent teeth.
The current mode of therapy for the dental anomalies is:
Surgical removal of supernumerary teeth.
Surgical exposure of permanent teeth.
Growth modulation of maxilla and mandible.
Delaire's Face mask and chin cup, as per the requirement.
Planned removal of non-resorbing primary teeth.
When growth is complete consideration of orthognathic surgery in severe skeletal Class III malocclusion cases.
NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
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