The wiki article on this syndrome is very interesting. Apparently there is a substantial number of people with this genetic deletion that are not diagnosed as they are cognitively normal. There does not seem to be a term for such 'mild' Williams syndrome like there is for autism.
There's a blurry line between 'diagnosed' and 'what kind of person you are' which is increasingly being encroached upon by modern medicine. Certainly there are lots of ways a person can be classified which only become a disorder when they go above a certain magnitude.
Progress will be made into better classifying people so that more and more regular folks can take advantage of strategies and 'treatments' to have a more successful life (whatever that may be). With this comes the risk of discrimination relying too heavily on these classifications, which, though real, will never be fair to judge a person against.
This is certainly true - we are all carrying various mutations that influence who we are. For example, I am now sitting in front of my computer drinking a chocolate milk - something I can only do as an adult because I have a mutated version of the lactase gene that causes lactase to be expressed in adulthood (lactase persistent syndrome). Until agriculture was invented this "syndrome" had negative value since unless I am drinking milk it is a waste of resources for my body to make an enzyme that won't be used.
As we learn more about each persons genome I hope we stop categorising people into people with a "syndrome" and those without.
