Just one in 7,500 babies is born with it, but help for these tiny victims could bring help to millions who suffer from hypertension and anxiety.
Seth Link has been banging that drum kit since he was toddler. Like many with Williams syndrome, he uses music for expression.
"You have all this energy, and all this stuff, and you want to be able to experience it, you know, and to share it with other people," Seth told Ivanhoe.
A missing piece on the 7th chromosome can lead to learning disabilities and heart trouble. Other traits are extreme friendliness and empathy, to the point of being less able to detect risky situations or ill intentions in others.
Seth needed heart surgery at just 10 months old. While extremely sociable, he suffers from high anxiety. But music ? any music? soothes his soul.
"If he starts getting anxious, we can ask him to think about his favorite song or go play some beats and get him immersed in that, and it does seem to help him control his anxiety," Becky Link, Seth's mom, told Ivanhoe.
Vanderbilt University is studying how music -- and more -- affects anxiety at this special camp for people with Williams syndrome.
"It's kind of a lesson in contradictions. How can people who have significant developmental disabilities also have pronounced and marked interest in music and musical talent?" Elisabeth Dykens, Ph.D., director, Vanderbilt Kennedy Center, told Ivanhoe.
The answer could lead to new treatments for all people with anxiety. Since Williams is genetic, research may pinpoint genes that trigger mental development and even personality issues. It's research Seth is proud to be a part of.
"Being yourself is sometimes the most important thing that a person can do," Seth told Ivanhoe.
National Williams Syndrome Awareness Week runs May 8-14. Because it can look like other disorders, experts say the majority of people with Williams have not been diagnosed yet.