Williams Syndrome is a genetic condition that affects between one in every 8,000 or 25,000 births, depending on which part of the world you live in or which website you get your information from. Either way, it's pretty rare and most people won't personally know someone who has Williams Syndrome. The syndrome was first described in 1961 by a Dr Williams based on a number of characteristics in people affected; basically four children all with aortic stenosis, learning difficulties and particular facial features. In the mid 1990s researchers were able to confirm that the root cause of WS was a small deletion on chromosome 7, that means, in people with WS, a piece of genetic material that contains about 25 different genes, is missing from one of their chromosomes.