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Diseases » Williams Syndrome » Wikipedia
 

Williams Syndrome in Wikipedia

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This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Williams syndrome". (Source - Retrieved 2006-09-07 14:13:14 from https://en.wikipedia.org/wiki/Williams_syndrome)

Introduction

Williams syndrome (also Williams-Beuren syndrome, sometimes called Pixieism) is a rare genetic disorder, occurring in fewer than 1 in every 20,000 live births.

Symptoms

It is characterized by a distinctive, "elfin" facial appearance along with a low nasal bridge, an unusually cheerful demeanor coupled with unpredictably occurring negative outbursts, ease with strangers, mental retardation coupled with an unusual facility with language, a love for music, cardiovascular problems such as supravalvular aortic stenosis, and transient hypercalcemia. Williams shares some features with autism, although persons with Williams syndrome generally possess very good social skills, to the point that this condition is sometimes called "cocktail party syndrome". Temple Grandin, author of Thinking in Pictures, has claimed that the brain abnormalities of Williams syndrome are the opposite of autism.$[1]$ There also appears to be a higher prevalence of left-handedness and left-eye dominance in those with the syndrome.$[2]$

Another symptom of Williams syndrome is lack of depth perception and inability to visualize how different parts assemble into larger objects (for example: assembling a jigsaw puzzle). This problem is caused by a slight defect in the brain that creates a sparsity of tissue in the visual systems of the brain. A team of researchers at the National Institute of Mental Health used functional magnetic resonance imaging (fMRI) to watch the blood flow of the brains of test subjects while they were performing two tasks involving spatial relations. Persons with Williams syndrome showed weaker activity in the section of the brain associated with spatial relations. Scans of brain anatomy of test subjects with Williams indicated a deficit of brain tissue in an area of the same section of the brain mentioned above. This deficit partially blocks transmission of visual information to the spatial relations region of the brain. In the test, all participants of the study measured in the average intelligence range to remove the possibility that the retardation aspect of Williams syndrome may have had an effect on the visual systems of the tested individuals.

Causes

Williams syndrome is caused by the deletion of genetic material from the region q11.2 of chromosome 7. The deleted region includes more than 20 genes, and researchers believe that the loss of several of these genes probably contributes to the characteristic features of this disorder. CYLN2, ELN, GTF2I, GTF2IRD1, and LIMK1 are among the genes that are typically deleted in people with Williams syndrome. Researchers have found that loss of the ELN gene, which codes for the protein elastin, is associated with the connective tissue abnormalities and cardiovascular disease (specifically SVAS) found in many people with this disease. Studies suggest that deletion of LIMK1, GTF2I, GTF2IRD1, and perhaps other genes may help explain the characteristic difficulties with visual-spatial tasks. Additionally, there is evidence that the loss of several of these genes, including CYLN2, may contribute to the unique behavioral characteristics, mental retardation, and other cognitive difficulties seen in Williams syndrome.

The relationship between other genes in the deleted region and the signs and symptoms of Williams syndrome is unknown.

 

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