Genetics Northern California

Crouzon Syndrome

Crouzon syndrome is a congenital condition that is diagnosed on the basis of a specific pattern of cranial and facial malformations. Craniosynostosis, or premature fusion of the cranial sutures, is the basic identifiable characteristic of a patient who has Crouzon syndrome (sometimes called craniofacial dysostosis). Crouzon syndrome is distinguished from other syndromes of craniosynostosis in that all of the findings are limited to the craniofacial skeleton. This fusion of the skull bones is accompanied by facial symptoms that include exopthalmos (small eye sockets), proptosis (protruding eyeballs), a beaked nose, a retruded midface, a protruding lower jaw, overcrowding of the teeth, and a narrow high arched palate or cleft palate. Like so many other craniofacial conditions, Crouzon syndrome is highly variable across cases; some people are mildly affected, while others have a more severe presentation.

Perhaps the most important concern for children with Crouzon syndrome is the inhibited growth of the brain that results from craniosynostosis. If the fused sutures are not surgically corrected, the child's brain will develop in abnormal directions. The anomalies of the midface can vary in severity. Some affected children will have difficulty breathing. The exopthalmos and proptosis are not usually medically significant, but often lead to social concerns of teasing, etc. The deformities of the jaw tend to enhance the midface hypoplasia and cause problems with the teeth. These can be corrected through various surgical procedures.

Other common symptoms of Crouzon syndrome are related to the ear (auditory) canals. Some children may have absent ear canals or deformities of the middle ear. Hearing loss and sleep apnea are not unusual.  Symptoms related to Type II may include vertebral malformations, digital fusion, and ankylosis of the elbow joints. A few patients experience a combination of valve blockages, eye disorders, respiratory dysfunction, and serious spinal deformities. Whether these are directly related to Crouzon syndrome is as of yet uncertain.

Causes/Types
Specific mutations in a gene called FGFR2 (fibroblast growth factor recpetor 2) cause Crouzon syndrome. The FGFR2 mutation may be inherited as a dominant trait from a parent who has the condition. However, in about 25 to 50% of cases, the mutation happens as a brand new genetic change (also called de novo or sporadic mutation). Crouzon syndrome occurs in roughly 1 in 25,000 newborns. 

Diagnosis
The diagnosis of Crouzon syndrome is made based on the clinical findings described above. DNA mutation testing is available in cases where the diagnosis is not clear, but is not needed to make the diagnosis in most cases.

Treatment/Services
As mentioned, the craniosynostosis is the primary concern for treatment in young children with Crouzon syndrome. Various surgeries are available, most of which remove and replace part of the skull bone to relieve pressure on the brain. The exopthalmos is more difficult to treat. Different surgeries are available that are categorized into non-orbital and orbital procedures. These surgeries are not usually completely corrective; most reduce the severity to varying degrees. The large jaw associated with the syndrome is relatively easy to treat and includes the removal of parts of the mandible. Orthodontic treatment is generally advantageous in relieving any overcrowding of the teeth.

The surgeries can be performed at different ages according to the child's growth and development, as well as to a craniofacial team's recommendations. Any child diagnosed with Crouzon syndrome should be thoroughly evaluated by a skilled craniofacial team.

Articulation disorders are common and usually related to dental malocclusion. Resonance may be hyponasal due to a small nasopharynx and nasal cavity. Both areas are treatable with orthognathic surgery or mid-face advancement. Hearing disorders, usually mild conductive hearing loss, are related to chronic middle ear disease and treatable with medical management.

RESOURCES:

Genetics Home Reference: Crouzon syndrome - General information about Crouzon syndrome provided by the National Library of Health. Also includes links to many related sites.

Crouzon Support Network - Information and support for individuals and families affected by Crouzon Syndrome and related craniofacial anomalies.

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Last Reviewed: July 23, 2009 by Kimberly Barr, M.S.