Noonan Syndrome
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What is Noonan syndrome?Noonan syndrome is a developmental disorder characterized by unusual facial characteristics, short stature, heart defects, bleeding problems, and skeletal malformations. Eye abnormalities occur in up to 95 percent of patients. Problems with language and speech are common. Most males with this disorder have undescended testicles (cryptorchidism). The majority of children diagnosed with Noonan syndrome have normal intelligence, but a small percentage have special educational needs, and some affected individuals are mildly mentally retarded. How common is Noonan syndrome?Noonan syndrome occurs in approximately 1 in 1,000 to 2,500 people. What genes are related to Noonan syndrome?Mutations in the KRAS and PTPN11 genes cause Noonan syndrome. Approximately 50 percent of individuals with Noonan syndrome have mutations in the PTPN11 gene. A small number of people with a severe or atypical type of Noonan syndrome have mutations in the KRAS gene. Individuals with KRAS mutations may show signs of other disorders that resemble Noonan syndrome, specifically cardiofaciocutaneous syndrome and Costello syndrome. These disorders are usually caused by changes in genes other than KRAS. Researchers are investigating whether these syndromes are distinct from each other or variations of the same disorder. The PTPN11 gene provides instructions for making a protein that is important for the proper formation of several types of body tissues during development. This protein also plays a role in cell division, cell specialization (the process by which cells mature to carry out specific functions), and cell movement. The KRAS gene provides instructions for making a protein that is also involved in cell growth and division, cell specialization, and tissue development. Mutations in either the PTPN11 gene or the KRAS gene cause the resulting protein to be continuously active, rather than switching on and off in response to signals that control growth and development. This constant activation causes the improper regulation of systems that control cell growth and division, leading to the characteristic features of Noonan syndrome. How do people inherit Noonan syndrome?This condition is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder. In some cases, an affected person inherits the mutation from one affected parent. Other cases may result from new mutations in the gene. These cases occur in people with no history of the disorder in their family.
Source: National Institutes of Health
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Study data from University of California, Department of Pediatrics update understanding of mental disorders
2007 MAR 5 -- New investigation results, "Deregulated Ras signaling in developmental disorders: new tricks for an old dog," are detailed in a study published in Current Opinion In Genetics & Development. According to recent research from the United States, "Ras proteins regulate cell proliferation, survival and differentiation and are constitutively activated by somatic point mutations in many cancers. Previous studies of neurofibromatosis type 1 and Noonan syndrome also implicated hyperactive Ras in developmental disorders." "Recently, germline mutations in H-RAS and K-RAS and in genes encoding other molecules in the Ras-Raf-MEK-ERK cascade were shown to underlie cases of Noonan, cardio-facio-cutaneous, and Costello syndromes. These disorders share phenotypic traits that include abnormal facial features, heart defects, and impaired growth and development. Many of these germline, disease-associated mutations encode novel Ras, Raf and MEK proteins," wrote S. Schubbert and colleagues, University of California, Department of Pediatrics. The researchers concluded: "These studies underscore a crucial role of Ras signaling in human development." Schubbert and colleagues published their study in Current Opinion In Genetics & Development (Deregulated Ras signaling in developmental disorders: new tricks for an old dog. Current Opinion In Genetics & Development, 2007;17(1):15-22). For additional information, contact S. Schubbert, University of California, Dept. of Pediatrics, 513 Parnassus Avenue, Room HSE-302, San Francisco, CA 94143 USA. Publisher contact information for the journal Current Opinion In Genetics & Development is: Current Biology Ltd., 84 Theobalds Rd., London WC1X 8RR, England. Keywords: United States, San Francisco, Mental Disorders, Mental Disorder. This article was prepared by Mental Health Weekly Digest editors from staff and other reports. Copyright 2007, Mental Health Weekly Digest via NewsRx.com.
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