Williams Syndrome

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What is Williams syndrome?

Williams syndrome is a developmental disorder that affects many parts of the body. This condition is characterized by mild to moderate mental retardation or learning disabilities, unique personality characteristics, distinctive facial features, and heart and blood vessel (cardiovascular) problems.

Most people with Williams syndrome have some degree of mental retardation. They typically do better on tasks that involve spoken language and memorization than on visual-spatial tasks such as writing and drawing. Affected individuals have outgoing, engaging personalities and tend to take an extreme interest in other people. Attention deficit disorder (ADD), problems with anxiety, and phobias are common among people with this disorder.

Young children with Williams syndrome have distinctive facial features including a broad forehead, a short nose with a broad tip, full cheeks, a wide mouth with full lips, and small, widely spaced teeth. In older children and adults, the face appears longer and more gaunt.

A form of cardiovascular disease called supravalvar aortic stenosis (SVAS) occurs frequently in people with Williams syndrome. SVAS is a narrowing of the large blood vessel that carries blood from the heart to the rest of the body (the aorta). If this condition is not treated, the aortic narrowing can lead to shortness of breath, chest pain, and heart failure. Other problems with the heart and blood vessels have also been reported in people with this disorder.

Additional signs and symptoms of Williams syndrome include abnormalities of connective tissue (tissue that supports the body's joints and organs) such as joint problems and soft, loose skin. Affected people may also have increased calcium levels in the blood (hypercalcemia) in infancy, developmental delays, problems with coordination, and short stature. Medical problems involving the eyes and vision, the digestive tract, and the urinary system are also possible.

How common is Williams syndrome?

Williams syndrome is an uncommon condition that occurs in an estimated 1 in 7,500 to 20,000 births.

What are the genetic changes related to Williams syndrome?

Williams syndrome is a chromosomal condition related to chromosome 7.

The CYLN2, ELN, GTF2I, GTF2IRD1, and LIMK1 genes are associated with Williams syndrome.

Williams syndrome is caused by the deletion of genetic material from a specific region 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 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.

Can Williams syndrome be inherited?

Most cases of Williams syndrome are not inherited, but occur as random events during the formation of reproductive cells (eggs or sperm) in a parent of an affected individual. These cases occur in people with no history of the disorder in their family.

Williams syndrome is considered an autosomal dominant condition because one copy of the altered chromosome 7 in each cell is sufficient to cause the disorder. In a small percentage of cases, people with Williams syndrome inherit the chromosomal deletion from a parent with the condition.

Source: National Institutes of Health

Research on Williams syndrome genetics published by scientists at Stanford University

"Behavioral data showed participants with WS to be significantly less accurate (p <0.042) together with a non-significant trend to be slower than the TD comparison group while performing the global processing task. fMRI data showed participants with WS to possess reduced activation in the visual and parietal cortices. Participants with WS also showed relatively normal activation in the ventral occipitotemporal cortex, but elevated activation in several posterior thalamic nuclei," wrote D. Mobbs and colleagues, Stanford University.

The researchers concluded: "These preliminary results largely confirm previous research findings and neural models implicating neurodevelopmental abnormalities in extended subcortical and cortical visual systems in WS, most notably dorsal-stream pathways."

Mobbs and colleagues published the results of their research in Developmental Medicine & Child Neurology (Reduced parietal and visual cortical activation during global processing in Williams syndrome. Developmental Medicine & Child Neurology, 2007;49(6):433-8).

For additional information, contact D. Mobbs, Stanford University School of Medicine, Dept. of Psychiatry and Behavioral Sciences, Stanford, CA 94305-5719 USA.

The publisher of the journal Developmental Medicine & Child Neurology can be contacted at: Cambridge University Press, 40 West 20th St., New York, NY 10011-4211, USA.

Keywords: United States, Stanford, Williams Syndrome Genetics, Genetics, Williams Syndrome.

This article was prepared by Life Science Weekly editors from staff and other reports. Copyright 2007, Life Science Weekly via NewsRx.com.