Williams syndrome (WS; also Williams-Beuren syndrome or WBS) is a rare neurodevelopmental disorder caused by a deletion of about 26 genes from the long arm of chromosome 7. It is characterized by a distinctive, “elfin” facial appearance, along with a low nasal bridge; an unusually cheerful demeanor and ease with strangers; mental retardation coupled with unusual (for persons who are diagnosed as mentally retarded) language skills; a love for music; and cardiovascular problems, such as supravalvular aortic stenosis and transient hypercalcaemia. The syndrome was first identified in 1961 by Dr. J. C. P. Williams of New Zealand. 
Individuals with Williams syndrome are highly verbal and sociable (having what has been described as a “cocktail party” type personality), but lack common sense and typically have inhibited intelligence. Individuals with WS hyperfocus on the eyes of others in social engagements. Phenotypically patients tend to have widely spaced teeth, a long philtrum, and flattened nasal bridge.
People with Williams syndrome often have hyperacusis and phonophobia which resembles noise-induced hearing loss, but this may be due to a malfunctioning auditory nerve. Individuals with the condition tend to demonstrate a love of music, and also appear significantly more likely to possess perfect pitch.
There also appears to be a higher prevalence of left-handedness and left-eye dominance in those with Williams. Individuals with Williams syndrome also report higher anxiety levels as well as phobia development, which may be associated with hyperacusis.
Williams syndrome is caused by the deletion of genetic material from the region q11.23 of chromosome 7. The deleted region includes more than 20 genes, and researchers believe that the loss of several of these genes probably contributes to the characteristic features of this disorder. CLIP2, ELN, GTF2I, GTF2IRD1, and LIMK1 are among the genes that are typically deleted in people with Williams syndrome. Researchers have found that loss of the ELN gene, which codes for the protein elastin, is associated with the connective-tissue abnormalities and cardiovascular disease (specifically supravalvular aortic stenosis (SVAS) and supravalvular pulmonary stenosis (SVPS)) found in many people with this syndrome. Studies suggest that deletion of LIMK1, GTF2I, GTF2IRD1, and perhaps other genes may help explain the characteristic difficulties with visual–spatial tasks. Additionally, there is evidence that the loss of several of these genes, including CLIP2, may contribute to the unique behavioral characteristics, learning disabilities, and other cognitive difficulties seen in Williams syndrome.