Williams syndrome

Overview
Williams syndrome (also Williams-Beuren syndrome) is a rare genetic disorder, occurring in fewer than 1 in 7,500 live births. It is characterized by a distinctive, "elfin" 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 unusual (for persons who are diagnosed as mentally retarded) language skills; a love for music; and cardiovascular problems, such as supravalvular aortic stenosis and transient hypercalcaemia. The syndrome was first identified in 1961 by Dr. J. C. P. Williams of New Zealand.

Symptoms
Williams syndrome shares some features with autism (such as difficulty understanding the state of mind of conversational partners ) and Fetal alcohol syndrome (e.g., certain facial features, possible mental retardation, and negative potential outbursts), although persons with Williams generally possess very good social skills, such that this condition is sometimes called "cocktail-party syndrome". There also appears to be a higher prevalence of left-handedness and left-eye dominance in those with Williams, and cases of absolute pitch appear to be significantly higher amongst those with the condition.

Relativity and perception
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. When asked to perform tasks involving spatial relations, with their brains scanned by fMRI, people with Williams Syndrome showed weaker activity in the dorsal area of the brain, which is along the top and back of the brain and associated with vision and spatial relations. (fMRI measures brain activity by measuring blood flow through different parts of the brain.)

When asked to copy a picture, those with Williams Syndrome drew the small details while those diagnosed with Down Syndrome drew the big picture. (Navon Task)

Cause
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. , ELN,, , and 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 syndrome. 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 CLIP2, may contribute to the unique behavioral characteristics, mental retardation, and other cognitive difficulties seen in Williams syndrome.