Also known as the Williams-Beuren syndrome, it is a rare disorder in which a small number of genes (estimated to be about 21) are deleted from a specific region of the seventh chromosome (7q11.23). It is characterized by physical abnormalities, mild to moderate intellectual impairment, and an outgoing, overly friendly personality. Perhaps with tongue in cheek, it was speculated that Sarah Palin has a type of personality that fits with Williams syndrome: she is talkative and very sociable, can perform well in public, but she does not seem to fully grasp the meaning of anything she says. Also: Mick Jagger has facial features of Williams syndrome according to some:
BBC news website overview report: http://www.bbc.co.uk/news/health-26888280
See Aortic hypoplasia, Chromosome, Configural processing, Developmental disorder, Elastin (gene), Limkinase 1 gene, Prosopagnosia, Supraalvular aortic stenosis (SVAS), Turner’s syndrome