About craniofacial dysostosis

What is craniofacial dysostosis?

Crouzon syndrome is a rare genetic disorder that may be evident at birth (congenital) or during infancy. The disorder is characterized by distinctive malformations of the skull and facial (craniofacial) region. Such abnormalities may vary greatly in range and severity from case to case, including among affected family members. However, in most infants with Crouzon syndrome, the fibrous joints between certain bones of the skull (cranial sutures) close prematurely (craniosynostosis). In addition, facial abnormalities typically include unusual bulging or protrusion of the eyeballs (proptosis) due to shallow eye cavities (orbits); outward deviation of one of the eyes (divergent strabismus or exotropia); widely spaced eyes (ocular hypertelorism); and a small, underdeveloped upper jaw (hypoplastic maxilla), with protrusion of the lower jaw (relative mandibular prognathism).

In some instances, Crouzon syndrome is inherited as an autosomal dominant trait. In other cases, affected individuals have no family history of the disease. In such instances, Crouzon syndrome is thought to result from new genetic changes (mutations) that occur randomly for unknown reasons (sporadically).

What are the symptoms for craniofacial dysostosis?

Babies with Crouzon syndrome can have symptoms like these:

  • short and wide or long and narrow head
  • enlarged forehead
  • widely spaced eyes
  • bulging eyeballs
  • crossed eyes (strabismus)
  • eyes that point in two different directions
  • vision loss
  • eyelids that slant downward
  • flattened cheeks
  • curved, beak-like nose
  • small, poorly developed upper jaw
  • short upper lip
  • protruding lower jaw
  • hearing loss
  • opening in the lip (cleft lip) or roof of the mouth (cleft palate)
  • crowded teeth
  • mismatched bite

These symptoms may be more severe in some babies than in others.

A small percentage of children with Crouzon syndrome also have a skin condition called acanthosis nigricans. This condition causes dark, thick, and rough patches of skin to form in folds like the armpits, neck, behind the knees, and groin.

What are the causes for craniofacial dysostosis?

Crouzon syndrome is caused by changes called mutations in one of the four FGFR genes. Usually it affects the FGFR2 gene, and less often the FGFR3 gene.

Genes carry the instructions for making the proteins that direct the body’s functions. Mutations can affect whatever functions a specific protein has.

FGFR2 codes for a protein called fibroblast growth factor receptor 2. As a baby develops in the womb, this protein signals bone cells to form. Mutations to this gene amp up the signal, increasing bone development and causing the baby’s skull to fuse too soon.

A baby only needs to inherit one copy of the gene mutation from a parent to get Crouzon syndrome. If you have this condition, each of your children has a fifty-fifty chance of inheriting it. This inheritance pattern is called autosomal dominant.

In about 25 to 50 percent of people with Crouzon syndrome, the gene mutation happens spontaneously. In these cases, babies don’t need to have a parent with Crouzon syndrome to get the disorder.

What are the treatments for craniofacial dysostosis?

Children with mild Crouzon syndrome may not need to be treated. Those with more severe cases should see craniofacial specialists, doctors who treat disorders of the skull and face.

In more severe cases, doctors can perform surgery to open up the sutures and give the brain room to grow. After the surgery, kids will need to wear a special helmet for a few months to reshape their skull.

Surgery can also be done to:

  • relieve pressure inside the skull
  • fix a cleft lip or palate
  • correct a malformed jaw
  • straighten crooked teeth
  • correct eye problems

Children with hearing problems can wear hearing aids to amplify sound. Kids with this condition may also need speech and language therapy.

What are the risk factors for craniofacial dysostosis?

Crouzon syndrome affects males and females. Some articles in the medical literature report that males are affected more often than females. Crouzon syndrome is estimated to affect about 1.6 in 100,000 people in the general population. All forms of craniosynostosis are estimated to affect about 1 in 2,000-2,5000 live births.

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