Williams syndrome
From Wikipedia, the free encyclopedia
| ICD-9 | 758.9 |
|---|---|
| OMIM | 194050 |
| DiseasesDB | 859 |
| MedlinePlus | 001116 |
| eMedicine | ped/2439 |
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.
Contents |
[edit] Symptoms
It is characterized by a distinctive, "elfish" facial appearance, along with a low nasal bridge; an unusually cheerful demeanor and ease with strangers, coupled with unpredictably occurring negative outbursts; mental retardation coupled with an unusual facility with language; a love for music; and cardiovascular problems, such as supravalvular aortic stenosis and transient hypercalcaemia. Williams syndrome shares some features with autism (such as difficulty understanding the state of mind of conversational partners[1]), although persons with Williams generally possess very good social skills, such 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 those of autism.[2] There also appears to be a higher prevalence of left-handedness and left-eye dominance in those with Williams.[3]
Another symptom of Williams syndrome is lack of depth perception and an inability to visualize how different parts assemble into larger objects (in assembling jigsaw puzzles, for example). This problem is caused by a 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 partly 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 would have an effect on the visual systems of the tested individuals.
An interesting experiment documented the fact that when shown a picture, Williams Syndrome people drew the small details while people with Downs Syndrome drew the big picture. Thus it can be generalized that people with Williams Syndrome "miss the forest for the trees".
[edit] 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 supravalvular aortic stenosis (SVAS) and supravalvular pulmonary stenosis (SVPS)) 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.
[edit] References
- ^ "Rare Disorder Offers Fresh Insight into Language" by Rhitu Chatterjee. National Public Radio. 10 Jul 2006 (text only). [1]
- ^ Interview with Temple Grandin at Wrong Planet Page accessed 5 October 2006
- ^ Van Strien JW, Lagers-Van Haselen GC, Van Hagen JM, De Coo IF, Frens MA, Van Der Geest JN. "Increased prevalences of left-handedness and left-eye sighting dominance in individuals with Williams-Beuren syndrome." J Clin Exp Neuropsychol. 2005 Nov;27(8):967-76. PMID 16207621.
