Cleidocranial dysplasia

What it is, symptoms and effects

From: MedlinePlus Genetics, National Library of Medicine

Cleidocranial dysplasia is a condition that primarily affects development of the bones and teeth. Signs and symptoms of cleidocranial dysplasia can vary widely in severity, even within the same family.

Individuals with cleidocranial dysplasia usually have underdeveloped or absent collarbones, also called clavicles ("cleido-" in the condition name refers to these bones). As a result, their shoulders are narrow and sloping, can be brought unusually close together in front of the body, and in some cases can be made to meet in the middle of the body. Delayed maturation of the skull (cranium) is also characteristic of this condition, including delayed closing of the growth lines where the bones of the skull meet (sutures) and larger than normal spaces (fontanelles) between the skull bones that are noticeable as "soft spots" on the heads of infants. The fontanelles normally close in early childhood, but they may remain open throughout life in people with this disorder. Some individuals with cleidocranial dysplasia have extra pieces of bone called Wormian bones within the sutures.

Affected individuals are often shorter than other members of their family at the same age. Many also have short, tapered fingers and broad thumbs; flat feet; knock knees; short shoulder blades (scapulae); and an abnormal curvature of the spine (scoliosis). Typical facial features include a wide, short skull (brachycephaly); a prominent forehead; wide-set eyes (hypertelorism); a flat nose; and a small upper jaw.

Individuals with cleidocranial dysplasia often have decreased bone density (osteopenia) and may develop osteoporosis, a condition that makes bones progressively more brittle and prone to fracture, at a relatively early age. Women with cleidocranial dysplasia have an increased risk of requiring a cesarean section when delivering a baby, due to a narrow pelvis preventing passage of the infant's head.

Dental abnormalities are very common in cleidocranial dysplasia and can include delayed loss of the primary (baby) teeth; delayed appearance of the secondary (adult) teeth; unusually shaped, peg-like teeth; misalignment of the teeth and jaws (malocclusion); and extra teeth, sometimes accompanied by cysts in the gums.

In addition to skeletal and dental abnormalities, people with cleidocranial dysplasia may have hearing loss and are prone to sinus and ear infections. Some young children with this condition are mildly delayed in the development of motor skills such as crawling and walking, but intelligence is unaffected.

Causes and biological mechanisms

From: MedlinePlus Genetics, National Library of Medicine

Cleidocranial dysplasia is usually caused by mutations in the RUNX2 gene. This gene provides instructions for making a protein that is involved in the development and maintenance of teeth, bones, and cartilage. Cartilage is a tough, flexible tissue that makes up much of the skeleton during early development. Most cartilage is later converted to bone (a process called ossification), except for the cartilage that continues to cover and protect the ends of bones and is present in the nose, airways, and external ears.

The RUNX2 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) and in the development of teeth.

The RUNX2 gene mutations that cause cleidocranial dysplasia 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 the normal development of bones, cartilage, and teeth, resulting in the signs and symptoms of cleidocranial dysplasia. In rare cases, individuals with a deletion of genetic material that includes RUNX2 and other nearby genes may experience additional features, such as developmental delay, resulting from the loss of these genes.

In about 30 percent of individuals with cleidocranial dysplasia, no mutation in the RUNX2 gene has been found. The cause of the condition in these individuals is unknown.

Inheritance and family implications

From: MedlinePlus Genetics, National Library of Medicine

This condition is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder. Some affected individuals inherit the mutation from one affected parent. Often the parent is mildly affected, and in some cases had not previously been recognized as having the disorder. Other cases result from new mutations in the gene. These cases occur in people with no history of the disorder in their family.

How common is it?

From: MedlinePlus Genetics, National Library of Medicine

Cleidocranial dysplasia occurs in approximately 1 per million individuals worldwide. It is likely underdiagnosed because many affected individuals have mild signs and symptoms.

Reported clinical features and what the terms mean

The following findings are associated with this condition in Orphanet. They are not a checklist for diagnosing yourself, and they do not all occur in every affected person. Some are examination, imaging or laboratory findings that cannot be recognised at home.

The frequency labels describe how often a finding was reported among people with the condition in the source. They do not give the chance that a person with that symptom has the condition. Definitions below reproduce HPO terminology; they explain the term, not the likely severity in an individual.

Abnormality of dental enamel · Very frequent (99-80%)

An abnormality of the dental enamel.

Abnormality of the dentition · Very frequent (99-80%)

Any abnormality of the teeth.

Carious teeth · Very frequent (99-80%)

Caries is a multifactorial bacterial infection affecting the structure of the tooth. This term has been used to describe the presence of more than expected dental caries.

Down-sloping shoulders · Very frequent (99-80%)

Low set, steeply sloping shoulders.

Frontal bossing · Very frequent (99-80%)

Bilateral bulging of the lateral frontal bone prominences with relative sparing of the midline.

High, narrow palate · Very frequent (99-80%)

The presence of a high and narrow palate.

Hypertelorism · Very frequent (99-80%)

Interpupillary distance more than 2 SD above the mean (alternatively, the appearance of an increased interpupillary distance or widely spaced eyes).

Hypoplasia of the zygomatic bone · Very frequent (99-80%)

Underdevelopment of the zygomatic bone. That is, a reduction in size of the zygomatic bone, including the zygomatic process of the temporal bone of the skull, which forms part of the zygomatic arch.

Other findings in the same source

From: Orphanet

Additional reported features include Large fontanelles (Very frequent (99-80%)); Micrognathia (Very frequent (99-80%)); Narrow chest (Very frequent (99-80%)); Recurrent respiratory infections (Very frequent (99-80%)); Short clavicles (Very frequent (99-80%)); Short stature (Very frequent (99-80%)); Skeletal dysplasia (Very frequent (99-80%)); Sloping forehead (Very frequent (99-80%)); Supernumerary tooth (Very frequent (99-80%)); Wormian bones (Very frequent (99-80%)). This is a selected summary, not a complete description of the condition.

Which doctor should you see?

The suggested department for discussing Cleidocranial dysplasia is Orthopaedics, with a orthopaedic specialist as the relevant type of clinician. General physician / Family Medicine; paediatrician for children. Referral depends on symptoms.

Additional services that may be relevant, depending on the findings, include: Clinical Genetics.

This is an editorial referral starting point. The appropriate clinic depends on the person’s age, symptoms, previous diagnosis and local services. The first clinician can decide whether another specialty or a team is needed; a department label does not confirm the diagnosis.

How to prepare for an assessment

Bring a short timeline of the main symptoms: when they first appeared, whether they are constant or episodic, what seems to change them, and how they affect daily activities. Include previous reports, discharge summaries, current medicines and supplements, allergies, and any relevant family history. A dated record is more useful than trying to match every feature in an online article.

Ask the clinician what is already established and what remains uncertain. If a test is suggested, ask what question it answers, what its limitations are and how the result would change the next step. The information here is not an instruction to arrange every possible test. In children, bring growth, developmental and school information if it is relevant to the concern.

• What explains the change in pain, movement or function?
• Which activities need adjustment while the diagnosis is being clarified?
• What are the roles of rehabilitation, observation and surgery in this situation?

Treatment discussions and follow-up

The material gathered for this draft does not provide a complete condition-specific treatment pathway for Cleidocranial dysplasia. That gap does not mean that treatment is unavailable. A clinician needs to establish the diagnosis and review current guidance before recommending medicines, procedures, rehabilitation or other support.

Before leaving the appointment, clarify the next review date, who will communicate results, and whom to contact if the situation changes. Discuss difficulties with sleep, work, school, mobility, eating or emotional wellbeing when these are relevant. Practical support may require coordination between the treating clinician and other services.

When to seek emergency help

Severe breathing difficulty, collapse, new stroke-like symptoms, a seizure that is prolonged or repeated without recovery, uncontrolled major bleeding, or an immediate risk of self-harm require emergency help. In India, call 112 or reach the nearest emergency department. This is a general, non-exhaustive warning list; it is not a condition-specific triage tool.