Williams syndrome is a genetic disorder characterized by developmental delay, unusual facial appearance, narrowing of the aorta (large artery that leaves the heart) and particular cognitive and personality profiles. It is a rare condition caused by missing part of the genetic material on one copy of chromosome 7. The problem is usually caused by a random mutation, so parents may not have any family history of the condition. However, a person with Williams syndrome has a 50% chance of passing the disorder on to each child. It occurs in about 1 in 20,000 births. One of the 25 missing genes is the gene that produces elastin, a protein that gives elasticity to blood vessels and other tissues in the body. It is likely that having only one copy of this gene results in the narrowing of blood vessels seen in this condition.
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