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What is Williams Syndrome?

written by: •edited by: Paul Arnold•updated: 12/4/2010

Williams syndrome is a rare genetic disorder that is characterized by a range of health and mental problems such as learning disabilities, cardiovascular issues, and unique personality traits. It is caused by a deletion of parts of the long arm of chromosome 7.

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    What is Williams Syndrome?

    Williams syndrome is a congenital disorder that can affect many parts of the body causing developmental and learning problems. Babies born with the syndrome may have a low birth weight and experience difficulties feeding and gaining weight.

    Children with the condition tend to have distinctive facial features, that have been described as "elfin". These include: -

    • Broad forehead
    • Upturned nose
    • Wide mouth with full lips
    • Widely spaced teeth
    • Low nasal bridge

    Amongst the first signs of the syndrome are heart and/or blood vessel abnormalities such as high blood pressure.

    A condition known as supravalvular aortic stenosis (SVAS) is frequently diagnosed. This is a narrowing of the aorta, the large blood vessel that takes blood from the heart to the rest of the body. If it is not treated it can lead to chest pain, breathing difficulties and eventually heart failure. In some individuals the narrowing is not severe and just needs monitoring.

    In addition there may also be connective tissue abnormalities that affect the joints, and calcium levels may be raised in babies.

    The incidence of Williams syndrome in the United States is 1 in 7,500 to 20,000 births.

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    Williams Syndrome Characteristics

    There can be mild forms of learning disabilities and problems with balance. Individuals also have difficulties with visual-spacial tasks such as drawing - there is a vague understanding of the concept of space. However, they can excel in other tasks that involve music and learning by rote.

    Other Williams syndrome characteristics in affected individuals are outgoing, engaging personalities. They will take a strong interest in others and are sensitive and polite. However, affected children may talk excessively, sometimes in an adult and inappropriate manner (called "cocktail party" personality). A 2005 study by researchers from UCLA provided the first detailed images of the brains of Williams syndrome individuals. Using magnetic resonance imaging they observed the cerebral cortex and found cortical thickening and complexity in the language areas which were not seen in controls.

    Attention deficit disorder (ADD) is frequently diagnosed, and phobias and anxieties are common.

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    What Causes Williams Syndrome?

    There are 20,000-25,000 genes in the human genome and Williams syndrome is caused by a deletion of about 25 of them from a specific region on chromosome 7. It is likely that the absence of a few of these genes (not all) causes the problems associated with Williams syndrome. Amongst the genes that are usually missing from affected individuals are CLIP2, ELN, and GTF21.

    CLIP2 - codes for a protein called CAP-GLY domain containing linker protein 2; it is believed to play a role in the structure and function of nerve cells.

    ELN - codes for a protein called elastin which is a major component of elastin fibres that provide strength and flexibility to connective tissue. Researchers have discovered that absence of ELN is associated with connective tissue problems and cardiovascular abnormalities.

    GTF1 - codes for two proteins called BAP-135 and TFII-I. BAP-135 has a role in the immune system and contributes to the activation of B cells in response to foreign invaders. TFII-I is a transcription factor that is active in the brain and other parts of the body. Some scientists think that it is involved in the regulation of calcium into cells. It has also been postulated that loss of the GTF1 gene is associated with the learning disabilities observed in Williams syndrome.

    At the time of writing (December 2009) the relationship between many of the deleted genes and Williams syndrome symptoms is unknown.

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    Treatment

    There is no cure for Williams syndrome, but it is important to note that many affected children and adults lead full and active lives. Treatments are geared toward alleviating the symptoms and managing complications as and when they appear. This includes treating high levels of blood calcium and physical therapy for joint stiffness.

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    References

    Understanding Williams Syndrome: Behavioral Patterns and Interventions by Eleanor Semel and Sue R.Rosner

    Williams Syndrome Genes - National Library of Medicine http://ghr.nlm.nih.gov/gene/CLIP2






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