How common is Williams syndrome?
Williams syndrome affects an estimated 1 in 7,500 to 20,000 people.
What are the genetic changes related to 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 25 genes, and researchers believe that a loss of several of these genes probably contributes to the characteristic features of this disorder.
CLIP2, 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 supravalvular aortic stenosis) found in many people with this disease. Studies suggest that deletion of CLIP2, GTF2I, GTF2IRD1, LIMK1, and perhaps other genes may help explain the characteristic difficulties with visual-spatial tasks, unique behavioral characteristics, and other cognitive difficulties seen in people with Williams syndrome. Loss of the GTF2IRD1 gene may also contribute to the distinctive facial features often associated with this condition.
Researchers believe that the presence or absence of the NCF1 gene on chromosome 7 is related to the risk of developing hypertension in people with Williams syndrome. When the NCF1 gene is included in the part of the chromosome that is deleted, affected individuals are less likely to develop hypertension. Therefore, the loss of this gene appears to be a protective factor. People with Williams syndrome whose NCF1 gene is not deleted have a higher risk of developing hypertension.
The relationship between other genes in the deleted region of chromosome 7 and the signs and symptoms of Williams syndrome is unknown.