Crouzon syndrome is a genetic disorder known as a branchial arch

Branchial arch

In the development of vertebrate animals, the pharyngeal arches are anlage for a multitude of structures. In humans, they develop during the fourth week in utero as a series of mesodermal outpouchings on the left and right sides of the developing pharynx...

 syndrome. Specifically, this syndrome affects the first branchial

First branchial arch

The first branchial arch, also called the first pharyngeal arch and mandibular arch, is the first of six branchial arches that develops in fetal life during the fourth week of development...

 (or pharyngeal) arch, which is the precursor of the maxilla

Maxilla

The maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...

 and mandible. Since the branchial arches are important developmental features in a growing embryo

Embryo

An embryo is a multicellular diploid eukaryote in its earliest stage of development, from the time of first cell division until birth, hatching, or germination...

, disturbances in their development create lasting and widespread effects.

Overview

This syndrome is named after Octave Crouzon

Octave Crouzon

Octave Crouzon, full name Louis Edouard Octave Crouzon was a French neurologist who was born in Paris. He received his doctorate from the University of Paris where he studied under famous physicians such as Paul Georges Dieulafoy , Joseph Babinski and Pierre Marie...

, a French

France

The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

 physician

Physician

A physician is a health care provider who practices the profession of medicine, which is concerned with promoting, maintaining or restoring human health through the study, diagnosis, and treatment of disease, injury and other physical and mental impairments...

 who first described this disorder. He noted the affected patients were a mother and her daughter, implying a genetic basis. First called "craniofacial dysostosis", the disorder was characterized by a number of clinical features. This syndrome is caused by a mutation in the fibroblast growth factor receptor II, located on chromosome 10.

Breaking down the name, "craniofacial

Craniofacial

Craniofacial may be used to describe certain congenital malformations, injuries, surgeons who subspecialize in this area, multi-disciplinary medical-surgical teams that treat and do research on disorders affecting this region, and organizations with interest in...

" refers to the skull

Human skull

The human skull is a bony structure, skeleton, that is in the human head and which supports the structures of the face and forms a cavity for the brain.In humans, the adult skull is normally made up of 22 bones...

 and face

Face

The face is a central sense organ complex, for those animals that have one, normally on the ventral surface of the head, and can, depending on the definition in the human case, include the hair, forehead, eyebrow, eyelashes, eyes, nose, ears, cheeks, mouth, lips, philtrum, temple, teeth, skin, and...

, and "dysostosis" refers to malformation of bone.

Now known as Crouzon syndrome, the disease

Disease

A disease is an abnormal condition affecting the body of an organism. It is often construed to be a medical condition associated with specific symptoms and signs. It may be caused by external factors, such as infectious disease, or it may be caused by internal dysfunctions, such as autoimmune...

 can be described by the rudimentary meanings of its former name. What occurs in the disease is that an infant's skull and facial bones, while in development, fuse early or are unable to expand. Thus, normal bone growth cannot occur. Fusion of different sutures leads to different patterns of growth of the skull. Examples include: trigonocephaly

Trigonocephaly

Trigonocephaly is a congenital condition of premature fusion of the metopic suture leading to a triangular shaped forehead. The merging of the two frontal bones leads to transverse growth restriction and parallel growth expansion...

 (fusion of the metopic suture), brachycephaly

Brachycephaly

Brachycephaly, also known as flat head syndrome, is a type of cephalic disorder. This can result from premature fusion of the coronal sutures or from external deformation . The coronal suture is the fibrous joint that unites the frontal bone with the two parietal bones of the skull. The parietal...

 (fusion of the coronal suture), dolichocephaly

Dolichocephaly

Dolichocephaly is another word for scaphocephaly, a condition where the head is longer than would be expected, relative to the width of the head.It can present in cases of Sensenbrenner syndrome, Sotos syndrome, as well as Marfan syndrome.-External links:...

 (fusion of the sagittal suture

Sagittal suture

The sagittal suture is a dense, fibrous connective tissue joint between the two parietal bones of the skull. The term is derived from the Latin word Sagitta, meaning "arrow". The derivation of this term may be demonstrated by observing how the sagittal suture is notched posteriorly, like an arrow,...

), plagiocephaly

Plagiocephaly

Plagiocephaly is a condition characterized by an asymmetrical distortion of the skull.-Causes:It is a common finding at birth and may be the result of a restrictive intrauterine environment. If there is premature union of skull bones, this is more properly called craniosynostosis...

 (unilateral premature closure of lambdoid and coronal suture

Coronal suture

The coronal suture is a dense, fibrous connective tissue joint that separates the frontal and parietal bones of the skull. At birth, the bones of the skull do not meet.-Pathology:...

s), oxycephaly

Oxycephaly

Oxycephaly, also known as turricephaly and high-head syndrome, is a type of cephalic disorder. This is a term sometimes used to describe the premature closure of the coronal suture plus any other suture, like the lambdoid, or it may be used to describe the premature fusing of all sutures. It should...

 (fusion of coronal

Coronal suture

The coronal suture is a dense, fibrous connective tissue joint that separates the frontal and parietal bones of the skull. At birth, the bones of the skull do not meet.-Pathology:...

 and lambdoidal sutures), Kleeblattschaedel (premature closure of all sutures).

Causes

Associations with mutations in the genes of FGFR2 and FGFR3

FGFR3

Fibroblast growth factor receptor 3 is a protein that in humans is encoded by the FGFR3 gene. FGFR3 has also been designated as CD333 .-Structure and function:-Disease linkage:...

 have been identified.

Heredity

Crouzon syndrome is autosomal dominant; children of a patient have a 50% chance of being affected.

Symptoms

As a result of the changes to the developing embryo, the symptoms are very pronounced features, especially in the face. Low-set ears are a typical characteristic, as in all of the disorders which are called branchial arch syndromes. The reason for this abnormality is that ears on a fetus are much lower than those on an adult. During normal development, the ears "travel" upward on the head; however, in Crouzon patients, this pattern of development is disrupted. Ear canal malformations are extremely common, generally resulting in some hearing loss. In particularly severe cases, Ménière's disease

Ménière's disease

Ménière's disease is a disorder of the inner ear that can affect hearing and balance to a varying degree. It is characterized by episodes of vertigo and tinnitus and progressive hearing loss, usually in one ear. It is named after the French physician Prosper Ménière, who, in an article published...

 may occur.

The most notable characteristic of Crouzon syndrome is cranial synostosis, as described above, but it usually presents as brachycephaly, which results in the appearance of a short and broad head. Exophthalmos

Exophthalmos

Exophthalmos is a bulging of the eye anteriorly out of the orbit. Exophthalmos can be either bilateral or unilateral . Measurement of the degree of exophthalmos is performed using an exophthalmometer...

 (bulging eye

Human eye

The human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth...

s due to shallow eye sockets after early fusion of surrounding bones), hypertelorism

Hypertelorism

Hypertelorism is an abnormally increased distance between two organs or bodily parts, usually referring to an increased distance between the orbits . In this condition the distance between the inner eye corners as well as the distance between the pupils is greater than normal...

 (greater than normal distance between the eyes), and psittichorhina (beak-like nose) are also symptoms. Additionally, a common occurrence is external strabismus

Strabismus

Strabismus is a condition in which the eyes are not properly aligned with each other. It typically involves a lack of coordination between the extraocular muscles, which prevents bringing the gaze of each eye to the same point in space and preventing proper binocular vision, which may adversely...

, which can be thought of as opposite from the eye position found in Down syndrome

Down syndrome

Down syndrome, or Down's syndrome, trisomy 21, is a chromosomal condition caused by the presence of all or part of an extra 21st chromosome. It is named after John Langdon Down, the British physician who described the syndrome in 1866. The condition was clinically described earlier in the 19th...

. Lastly, hypoplastic maxilla

Hypoplastic maxilla

Hypoplastic maxilla is the name given to the dysfunctional structural condition around which the oral disruption literally pivoted. It is associated with Crouzon syndrome....

 (insufficient growth of the midface) results in relative mandibular prognathism (chin appears to protrude despite normal growth of mandible) and gives the effect of the patient having a concave face. Crouzon syndrome is also associated with PDA( patent ductus arteriosus) and aortic coarctation.

For reasons that are not entirely clear, most Crouzon patients also have noticeably shorter humerus

Humerus

The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....

 and femur

Femur

The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...

 bones relative to the rest of their bodies than members of the general population. A small percentage of Crouzon patients also have what is called "Type II" Crouzon syndrome, distinguished by partial syndactyly

Syndactyly

Syndactyly is a condition wherein two or more digits are fused together. It occurs normally in some mammals, such as the siamang and kangaroo, but is an unusual condition in humans.-Classification:...

.

Diagnosis

Diagnosis of Crouzon syndrome usually can occur at birth by assessing the signs and symptoms of the baby. Further analysis, including radiographs, magnetic resonance imaging

Magnetic resonance imaging

Magnetic resonance imaging , nuclear magnetic resonance imaging , or magnetic resonance tomography is a medical imaging technique used in radiology to visualize detailed internal structures...

 (MRI) scans, genetic testing, X-rays and CT scans can be used to confirm the diagnosis of Crouzon syndrome.

Incidence

Incidence of Crouzon syndrome is currently estimated to occur in 1 out of every 25,000 people out of the general population. There is a greater frequency in families with a history of the disorder, but that doesn't mean that everyone in the family is affected (as referred to above).

Treatment

Surgery

Craniofacial surgery

Craniofacial surgery is a surgical subspecialty of maxillofacial surgery, plastic surgery, and ENT that deals with congenital and acquired deformities of the skull, face, and jaws. Although craniofacial treatment often involves manipulation of bone, craniofacial surgery is not tissue-specific,...

 is typically used to prevent the closure of sutures of the skull from damaging the brain's development. Without surgery, blindness and mental retardation are typical outcomes. Craniofacial surgery

Craniofacial surgery

Craniofacial surgery is a surgical subspecialty of maxillofacial surgery, plastic surgery, and ENT that deals with congenital and acquired deformities of the skull, face, and jaws. Although craniofacial treatment often involves manipulation of bone, craniofacial surgery is not tissue-specific,...

 is a discipline of plastic surgery

Plastic surgery

Plastic surgery is a medical specialty concerned with the correction or restoration of form and function. Though cosmetic or aesthetic surgery is the best-known kind of plastic surgery, most plastic surgery is not cosmetic: plastic surgery includes many types of reconstructive surgery, hand...

. To move the orbits forward, craniofacial surgeons expose the skull and orbits and reshape the bone. To treat the midface deficiency, craniofacial surgeons can move the lower orbit and midface bones forward For jaw surgery, either plastic surgeons or oral and maxillofacial (OMS) surgeons have experience to perform these operations. It is rare to wear a custom-fitted helmet (or cranial band) for several months after surgery as that is only for single-suture "strip craniectomy" repair. Crouzon patients tend to have multiple sutures involved, most specifically bilateral coronal craniosynostoses, therefore an open operation is used rather than the strip craniectomy with helmeting.

Once treated for the cranial vault symptoms, Crouzon patients generally go on to live a normal lifespan.

Dental significance

For dentist

Dentist

A dentist, also known as a 'dental surgeon', is a doctor that specializes in the diagnosis, prevention, and treatment of diseases and conditions of the oral cavity. The dentist's supporting team aides in providing oral health services...

s, this disorder is important to understand since many of the physical abnormalities are present in the head, and particularly the oral cavity. Common features are a narrow/high-arched palate, posterior bilateral crossbite, hypodontia

Hypodontia

In dentistry, hypodontia is the condition at which the patient has missing teeth as a result of their failure to develop. Hypodontia describes a situation where the patient is missing up to 6 teeth, excluding the 3rd molars. Missing third molars occur in 9-30% of population...

 (missing some teeth), and crowding of teeth

Tooth

Teeth are small, calcified, whitish structures found in the jaws of many vertebrates that are used to break down food. Some animals, particularly carnivores, also use teeth for hunting or for defensive purposes. The roots of teeth are embedded in the Mandible bone or the Maxillary bone and are...

. Due to maxillary hypoplasia, Crouzon patients generally have a considerable permanent underbite and subsequently cannot chew using their incisors. For this reason, Crouzon patients sometimes eat in an unusual way--eating fried chicken with a fork, for example, or breaking off pieces of a sandwich rather than taking a bite in it.

External links

• GeneReviews/NIH/NCBI/UW entry on FGFR-Related Craniosynostosis Syndromes
• Crouzon Syndrome - About.com
  About.com
  About.com is an online source for original information and advice. It is written in English, and is aimed primarily at North Americans. It is owned by The New York Times Company....
  
  
• Crouzon Syndrome - Seattle Children's Hospital Craniofacial Center
• cleftAdvocate - Non-profit support organization for all craniofacial conditions; on-line and in-person family support, insurance and advocacy assistance, and more.
• General Information at hopkinsmedicine.org