Title: Cognitive and Behavioral Manifestations in Turner Syndrome
Abstract:Turner Syndrome (TS) is a common genetic disorder that affects approximately 1 in 1,900 live female births. Like other sex chromosome abnormalities (SCAs), TS has high morbidity due to associated cong...Turner Syndrome (TS) is a common genetic disorder that affects approximately 1 in 1,900 live female births. Like other sex chromosome abnormalities (SCAs), TS has high morbidity due to associated congenital abnormalities, neurodevelopmental disturbances, neurocognitive deficits, and social-behavioral problems. Many individuals with TS are not diagnosed. Those who are identified may be subject to inadequate care, bias, and discrimination because of a poor understanding of the condition among families, health care providers, and educators, especially regarding developmental profiles and outcomes. Turner syndrome results from an abnormal or missing second sex (i.e., X) chromosome, and by definition, affects only females. There is tremendous variability in the clinical presentations of individuals with TS that is likely due to the variable nature of the genetic abnormality. Approximately 50% of girls with TS have a 45X karyotype (Savendahl and Davenport 2000; Soriano-Guillen et al. 2005; Sybert and McCauley 2004), with the remainder having either a structural abnormality or mosaicism involving the X chromosome. Structural changes of the X chromosome include deletions, breakage of both arms to form a ring chromosome, or breakage and exchange in the X centromere region to form an isochromosome. Common mosaic patterns include 45,X/46,XX, 45,X/46,X,i(X), and 45, X/46,XY (Table 19.1). Correlations of clinical phenotype with cytogenetic data are further complicated by the wide range of structural abnormalities, as well as by mosaicism, differences in X-inactivation patterns, and the presence of abnormal recessive genes (Ogata and Matsuo 1995). Girls with 45X karyotype tend to be most severely affected, and there is less variability within this group than in the population as a whole. Many of the clinical manifestations of TS can be understood in the context of reduced expression of genes on the X chromosome (Neely 1994; Zinn and Ross 1998; Zinn et al. 1998). In normal females, one X chromosome is inactivated; however, the process is not complete. Genes on the X-chromosome that are not inactivated, so-called pseudoautosomal genes, are present in a cluster near the tip of the short arm and scattered elsewhere.Read More
Publication Year: 2010
Publication Date: 2010-04-29
Language: en
Type: book-chapter
Indexed In: ['crossref']
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