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Roberts syndrome, or sometimes called ''pseudothalidomide syndrome'', is an extremely rare genetic disorder that is characterized by mild to severe prenatal retardation or disruption of cell division, leading to malformation of the bones in the skull, face, arms, and legs. Roberts syndrome is also known by many other names, including: Hypomelia-Hypotrichosis-Facial Hemangioma Syndrome, SC Syndrome (once thought to be an entirely separate disease), Pseudothalidomide Syndrome, Roberts-SC Phocomelia Syndrome, SC Phocomelia Syndrome, Appelt-Gerken-Lenz Syndrome, RBS, SC Pseudothalidomide Syndrome, and Tetraphocomelia-Cleft Palate Syndrome.〔Kugler, Mary. ("Roberts syndrome: Inherited Disorder Causes Abnormal Bone Development." ) About.com: Rare Diseases. Published 23 April 2005. Accessed 13 March 2010〕〔Francke, Uta, and Jinglan Liu. ("Roberts syndrome." ) National Organization for Rare Disorders. Published 26 November 2008.〕〔〔("Roberts syndrome." ) Genetics Home Reference. 2010. U.S. National Library of Medicine. 13 March 2010.〕 It is a genetic disorder caused by the mutation of the ESCO2 gene on 8th chromosome. Named after John B. Roberts, who first described the syndrome in 1919, it is one of the rarest autosomal recessive disorders, affecting approximately 150 known individuals. The Syndrome is both autosomal, in that there are equal numbers of copies of the gene in both males and females, and recessive, meaning the child must inherit the defective gene from both parents. The mutation causes cell division to occur slowly or unevenly, and the cells with abnormal genetic content die. Roberts syndrome can affect both males and females. Although the disorder is rare, the affected group is diverse. The mortality rate is high in severely affected individuals. ==Heredity== ESCO2, located on human chromosome 8, has been labeled as the gene responsible for Roberts syndrome. In fact, ESCO2 is the only known gene that has demonstrated RBS-causing mutations. Also, all individuals that have been cytogenetically diagnosed with Roberts syndrome have also had mutations in the ESCO2 gene.〔 In order to contract Roberts syndrome, a child must inherit the defective gene in an autosomal recessive manner. In other words, the child must inherit two copies of the defective gene (one from each parent). The ESCO2 gene has a specific effect on cell division in Roberts syndrome patients. In normal cell division, each chromosome is copied and then attached to its newly formed copy at the centromere (the center portion of a chromosome). However, in Roberts syndrome cell division, the copies are frequently not attached at the centromere. As a result, the chromosomes do not get lined up properly, which causes the cell to divide very slowly or even to not divide at all. The new cells typically will have too many or too few chromosomes. The odd number of chromosomes causes the defective cells to die, which leads to the malformations associated with Roberts syndrome.〔 Many of the physical malformations associated with Roberts syndrome are very similar to the malformations that occur in children whose mothers took thalidomide during pregnancy. The physical similarities suggest that there is a similar underlying biology between ESCO2 and thalidomide. As a result, it is speculated that thalidomide affects chromosomes and cell division in a similar manner to ESCO2. For this reason, Roberts syndrome is sometimes called Pseudothalidomide Syndrome. 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「Roberts syndrome」の詳細全文を読む スポンサード リンク
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