Williams Syndrome
Everyone has heard of Downs Syndrome, and we can recognize anyone with it. There is another syndrome with a similar cause that is less common, and less widely known – I’ve only just heard about it myself: Williams Syndrome.
It is also known as elfin syndrome, because those with it look like elves, supposedly. From looking in Google Image Search, I think a more modern definition would be to relate them to The Joker from Batman:
What really fascinates me about these people is, according to a scientific article I recently read, on top of having traits like highly verbal and overly sociable, having what has been described as a “cocktail party” type personality and hyperfocus on the eyes of others in social engagements, they tend to trust everyone they meet.
With estimates of 1 in 7,500 to 1 in 20,000 births, there is quite likely a Williams Syndrome person in your town or suburb. You may have even interacted with them, without realising that they have a genetic disorder that explains their different behaviour.