|
Edwards syndrome (also known as trisomy 18 ()) is a chromosomal abnormality caused by the presence of all, or part of, an extra 18th chromosome. This genetic condition almost always results from nondisjunction during meiosis. It is named after John Hilton Edwards, who first described the syndrome in 1960.〔(【引用サイトリンク】title=Edwards syndrome (John Hilton Edwards) )〕 It is the second-most common autosomal trisomy, after Down syndrome, that carries to term. Edwards syndrome occurs in around one in 6,000 live births, and around 80% of those affected are female. The majority of fetuses with the syndrome die before birth.〔 The incidence increases as the mother's age increases. The syndrome has a very low rate of survival, resulting from heart abnormalities, kidney malformations, and other internal organ disorders. ==Signs and symptoms== Children born with Edwards syndrome may have some or all of these characteristics: kidney malformations, structural heart defects at birth (i.e., ventricular septal defect, atrial septal defect, patent ductus arteriosus), intestines protruding outside the body (omphalocele), esophageal atresia, intellectual disability, developmental delays, growth deficiency, feeding difficulties, breathing difficulties, and arthrogryposis (a muscle disorder that causes multiple joint contractures at birth).〔〔(【引用サイトリンク】title=Trisomy 18 )〕 Some physical malformations associated with Edwards syndrome include small head (microcephaly) accompanied by a prominent back portion of the head (occiput), low-set, malformed ears, abnormally small jaw (micrognathia), cleft lip/cleft palate, upturned nose, narrow eyelid folds (palpebral fissures), widely spaced eyes (ocular hypertelorism), drooping of the upper eyelids (ptosis), a short breast bone, clenched hands, choroid plexus cysts, underdeveloped thumbs and/or nails, absent radius, webbing of the second and third toes, clubfoot or rocker bottom feet, and in males, undescended testicles.〔(【引用サイトリンク】title=What is Trisomy 18? )〕〔 ''In utero'', the most common characteristic is cardiac anomalies, followed by central nervous system anomalies such as head shape abnormalities. The most common intracranial anomaly is the presence of choroid plexus cysts, which are pockets of fluid on the brain. These are not problematic in themselves, but their presence may be a marker for trisomy 18. Sometimes, excess amniotic fluid or polyhydramnios is exhibited.〔 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「Edwards syndrome」の詳細全文を読む スポンサード リンク
|