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Crouzon syndrome is an autosomal dominant genetic disorder known as a branchial arch syndrome. Specifically, this syndrome affects the first branchial (or pharyngeal) arch, which is the precursor of the maxilla and mandible. Since the branchial arches are important developmental features in a growing embryo, disturbances in their development create lasting and widespread effects. This syndrome is named after Octave Crouzon,〔L. E. O. Crouzon. Dysostose cranio-faciale héréditaire. Bulletin de la Société des Médecins des Hôpitaux de Paris, 1912, 33: 545-555.〕 a French physician 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" refers to the skull and face, and "dysostosis" refers to malformation of bone. Now known as Crouzon syndrome, the disease 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 (fusion of the metopic suture), brachycephaly (fusion of the coronal suture), dolichocephaly (fusion of the sagittal suture), plagiocephaly (unilateral premature closure of lambdoid and coronal sutures), oxycephaly (fusion of coronal and lambdoidal sutures), Kleeblattschaedel (premature closure of all sutures). ==Signs and 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 foetus 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 may occur. The most notable characteristic of Crouzon syndrome is craniosynostosis, as described above; however it usually presents as brachycephaly resulting in the appearance of a short and broad head. Exophthalmos (bulging eyes due to shallow eye sockets after early fusion of surrounding bones), hypertelorism (greater than normal distance between the eyes), and psittichorhina (beak-like nose) are also symptoms. Additionally, external strabismus is a common occurrence, which can be thought of as opposite from the eye position found in Down syndrome. Lastly, hypoplastic maxilla (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 patent ductus arteriosus (PDA) and aortic coarctation. For reasons that are not entirely clear, most Crouzon patients also have noticeably shorter humerus and femur 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. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Crouzon syndrome」の詳細全文を読む スポンサード リンク
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