Overly friendly (excessively social) personality
Individuals with Williams syndrome have a very endearing personality. They have a unique strength in their expressive language skills, and are extremely polite. They are typically unafraid of strangers and show a greater interest in contact with adults than with their peers.
~ Williams Syndrome Association

So it's possible to be "overly friendly", and that is a disease. Is sociability genetic? Do I have an AS gene?