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Crouzon syndrome is an autosomal dominant genetic disorder. This genetic disorder causes abnormal growth of the midface, eye sockets, and craniosynostosis. Breaking down the name, "craniofacial" refers to the skull and face, and "dysostosis" refers to malformation of bone. This syndrome causes premature fusion of the calvarial suture and cranial bones. In addition, there are abnormalities associated with the mid-face and malocclusion of the teeth. This syndrome is caused by a mutation of the FGFR2 genes that are vital in embryonic development.[1]

Crouzon syndrome was first discovered by a French neurosurgeon in 1912 when he diagnosed his patients; a mother and child with the abnormal facial features he discovered.[2]

Crouzon syndrome is slightly different from other craniosynostosis syndromes because there aren't any abnormalities associated with the extremities of the child/individual. However, there can potentially be an issue with the spine causing additional anomalies in other areas such as the elbow or internal organs.

Other names used for Crouzon syndrome is craniofacial dysarthrosis, craniofacial dysostosis, and craniofacial dysostosis syndrome. The names mentioned all have relevance to the original name of the disease.

In addition, this disease expected to be diagnosed in more than 16 million new born's a year. Also, Crouzon syndrome is one of the most common crainsynostosis diseases diagnosed in infants. Although this disease is more commonly found in Caucasian's, this genetic disorder can occur in any race.

Signs and symptoms

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Although there aren't any specific warning signs and symptoms associated with Crouzon syndrome besides past family history of the genetic disorder. Genetic changes of information during embryonic development makes the disease hard to detect.

The most noticeable signs can be seen in the face of the child which are chronic. The symptoms would include the back and top of the head to not be shaped properly causing the head to be flattened. The head is also flattened on the forehead as well as the temple. In addition to portions of the head being flattened, the mid face of the child is lower than normal and the face tends to look as if it's pushed back into the cranium with protrusion of the eyes. The nose would also be beaked shaped and the due to the extreme pressure on the nasal passages, getting oxygen through the nasal passages is difficult.[3]

Also, there is a malocclusion due to the improper shape of the skull causing the teeth of the individual not to be aligned properly. Due to the malocclusion, the individual's roof of mouth may be higher or taller than normal causing the teeth of the upper mandible to go behind the teeth on the lower mandible during chewing. [4]

Another symptom is the ears of the child are positioned lower than normal due to the disrupted pattern of development. Because of the improper development, the most common issue associated with the ears in a lower position is hearing loss. Although hearing loss is likely to happen, there are more symptoms including Ménière's disease that causes ringing of the ears and light-headedness, and ring of the ears. Poor vision is also a common symptom of Crouzon's disease. The individual can experience involuntary eye movement and being crossed eyed as well[5].

There has also been reports of individuals suffering from Acanthosis Nigricans which is small, dark, patches of the skin in folds of the body. In addition, there have been few reports of individuals suffering from hydrocephalus which is build up of fluid in the cranium.

The joints of individuals suffering from Crouzon syndrome have been know to function properly but in some cases, there is limited mobility of elbow movement.

Causes/Mechanism

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Crouzon syndrome is caused by a mutation of ( Fibroblast growth factor receptor 2) FGFR2[6] and (Fibroblast growth factor receptor 3) FGFR3[7] which have been identified as the culprit genes for this rare genetic disease.[8][9] Although, not clear on why these genes mutate; however, the mutated genes can be passed down to offspring. The function of the FGFR2 and FGFR3 genes is to play a very important role during embryonic development. These genes are vital to embryonic development because of their role in the cell pertains to how well the cell is regulated in terms of carrying out specific functions, maturation, cell divison, and other important functions such as angiogenesis.[10] When the FGFR2 and FGFR3 signals for immature cells to become skeletal cells, one end stays inside the cell while the other end extends out from the cell surface allowing for the protein to receive a signal for specific growth factors from the cytoplasm. Once the protein receive signal, these specific growth factors will begin to undergo the changes necessary to become the specialized function it was intended to be such as a skeletal muscle. In addition, due to FGFR2 and FGFR3 genes playing vital roles in bone growth during embryonic development, the premature signalling of this protein is the primary cause of the calvarial and cranial bone fusing together inducing the rare genetic disorder; Crouzon syndrome.

Diagnosis

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Crouzon's syndrome is usually diagnosed by physically checking the child's structure of head and extremities signs and symptoms of the genetic disorder. Other diagnosis include CT scans, MRI, And X rays.  A CT scan is an X-ray procedure that takes a computer-enhanced cross-sectional view of the body. An MRI will give the doctor a better look at the internal structures of the cranium. And the X rays will allow to the doctor to examine the bones of the individual. The doctor would take images of the head and extremities to give a correct diagnosis. After the doctor has examined the head structure and images, sh/she will be able to determine if in fact Crouzon syndrome is the proper diagnosis as well conclude if any sutures have fused together.[11]

Other diagnosis include the the doctor the taking samples of the skin to detect if there is a presence of Acanthosis nigricans. An additional diagnosis test the doctor will conduct is a genetic test to determine if the child and/or parent has in fact been affected by a gene mutation of the FGFR2 gene. If there is not presence of a mutated gene, doctors will assume that there has been a spontaneous mutation.[12]

There are currently no known ways to prevent Crouzon's disease.

Treatment

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A child with Crouzon syndrome wearing a corrective cranial band.

The most common way to treat Crouzon's syndrome is to treat this genetic disorder with surgery.There are several surgical ways that will help treat Crouzon's syndrome. The most common is craniectomy and this type of surgery involves portions of the skull being removed and/ reshaped that will allow for the brain to have adequate space to develop as well as remove any closed sutures. Performing this technique early as possible will ensure that there is a less chance of the infant being diagnosed with mental retardation later in life.[13] Also, plastic surgeons can perform a procedure that will adjust the bones of the surrounding orbitals that are effected in order to help alleviate protrusion of the eyeballs to prevent additional inter-cranial pressure. [14]

In addition, a midface advancement (Also know as Lefort III midface advancement) may also be an option if it is conducted early. During this procedure, portions of the mid face will be bought forward along with the upper and lower jaw. This allows for the bite of the individual to be corrected as well as the airway used for breathing to open more and allow for more oxygen in the body.[15]

For the teeth, seeing an orthodontist to remove excessive teeth will help prevent over-crowding in the mouth. Also, braces are recommended to help the alignment of the teeth.

To correct or prevent any hearing loss as well as any speech impediment, regular check-ups are recommended. If there is a hearing issue, a hearing aid can be used to assist the individual's hearing.

Correcting some of these issue will almost guarantee that a full life can be lived. If some of these issues are not corrected, the parent would have to ensure that regular check-ups are conducted to ensure that there is not are not any major health issues such as hydrocephalus, sleep apnea, and mental retardation.

Relevant Research

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Recent research has been conducted to determine exactly what causes the FGR2 gene to spontaneously mutate. The research determined that the FGR2 gene is a missense mutation. A missense mutation occurs when there is a substitution of amino acids in the final protein product. When this happens, the outcome of the protein can have no effect and be non-functional or can cause a change in the phenotype and/or genotype of the organism. In this case, the missense mutation causes premature fusion of the cranial sutures.[16]

See also

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References

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  1. ^ "Crouzon syndrome". {{cite journal}}: Cite journal requires |journal= (help)
  2. ^ "Genetics of Crouzon Syndrome: Background, Pathophysiology, Epidemiology". {{cite journal}}: Cite journal requires |journal= (help)
  3. ^ "Crouzon syndrome". {{cite journal}}: Cite journal requires |journal= (help)
  4. ^ "Crouzon syndrome". Genetics Home Reference. 2015-12-07. Retrieved 2015-12-09.
  5. ^ "Genetics of Crouzon Syndrome Clinical Presentation: History, Physical, Causes". emedicine.medscape.com. Retrieved 2015-12-09.
  6. ^ Reardon W, Winter RM, Rutland P, Pulleyn LJ, Jones BM, Malcolm S (September 1994). "Mutations in the fibroblast growth factor receptor 2 gene cause Crouzon syndrome". Nat. Genet. 8 (1): 98–103. doi:10.1038/ng0994-98. PMID 7987400.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  7. ^ Meyers GA, Orlow SJ, Munro IR, Przylepa KA, Jabs EW (December 1995). "Fibroblast growth factor receptor 3 (FGFR3) transmembrane mutation in Crouzon syndrome with acanthosis nigricans". Nat. Genet. 11 (4): 462–4. doi:10.1038/ng1295-462. PMID 7493034.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  8. ^ James, William; Berger, Timothy; Elston, Dirk (2005). Andrews' Diseases of the Skin: Clinical Dermatology. (10th ed.). Saunders. ISBN 0-7216-2921-0.
  9. ^ Vajo Z, Francomano CA, Wilkin DJ. (February 2000). "The molecular and genetic basis of fibroblast growth factor receptor 3 disorders: the achondroplasia family of skeletal dysplasias, Muenke craniosynostosis, and Crouzon syndrome with acanthosis nigricans". Endocrine Reviews. 21 (1): 23–39. doi:10.1210/er.21.1.23. PMID 10696568.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  10. ^ "FGFR2 gene". Genetics Home Reference. 2015-12-07. Retrieved 2015-12-09.
  11. ^ "Genetics of Crouzon Syndrome Clinical Presentation: History, Physical, Causes". emedicine.medscape.com. Retrieved 2015-12-10.
  12. ^ "Crouzon Syndrome Information - The Mount Sinai Hospital". The Mount Sinai Hospital. Retrieved 2015-12-10.
  13. ^ "Crouzon Syndrome Treatment | Seattle Children's Hospital". www.seattlechildrens.org. Retrieved 2015-12-10.
  14. ^ "Crouzon Syndrome Information - The Mount Sinai Hospital". The Mount Sinai Hospital. Retrieved 2015-12-10.
  15. ^ "Crouzon Syndrome Treatment | Seattle Children's Hospital". www.seattlechildrens.org. Retrieved 2015-12-10.
  16. ^ Rutland, Paul; Pulleyn, Louise J.; Reardon, William; Baraitser, Michael; Hayward, Richard; Jones, Barry; Malcolm, Sue; Winter, Robin M.; Oldridge, Michael (1995-02-01). "Identical mutations in the FGFR2 gene cause both Pfeiffer and Crouzon syndrome phenotypes". Nature Genetics. 9 (2): 173–176. doi:10.1038/ng0295-173.
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Wikimedia Commons has media related to Crouzon syndrome.

Category:Genodermatoses Category:Syndromes Category:Congenital disorders of musculoskeletal system Category:Cell surface receptor deficiencies Category:Rare diseases Category:Congenital oral disorders

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