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Williams syndrome (WS or WMS; also Williams–Beuren syndrome or WBS) is a rare neurodevelopmental disorder characterized by a distinctive, "elfin" facial appearance, along with a low nasal bridge, an unusually cheerful demeanor and ease with strangers; developmental delay coupled with strong language skills; and cardiovascular problems.
It is caused by a deletion of about 26 genes from the long arm of chromosome 7. The syndrome was first identified in 1961 by New Zealander Dr. J. C. P. Williams and has an estimated prevalence of 1 in 7,500 to 1 in 20,000 births.
Individuals with Williams syndrome often have hyperacusia and phonophobia which resembles noise-induced hearing loss, but this may be due to a malfunctioning auditory nerve. However, individuals with WS can also tend to demonstrate a love of music, and appear significantly more likely to possess perfect pitch. There also appears to be a higher prevalence of left-handedness and left-eye dominance.
Ophthalmologic issues are common in Williams syndrome. Up to 75% of subjects in some studies have strabismus (ocular misalignment), particularly esotropia, due to inherent subnormal binocular visual function. and cognitive deficits in visuospatial construction.
In addition, people with Williams syndrome often exhibit gross motor difficulties, including trouble walking down stairs, as well as overactive motor reflexes (hyperreflexia) and hyperactive, involuntary movement of the eyes (nystagmus).
Increased volume and activation of the left auditory cortex has been observed in people with Williams Syndrome, which has been interpreted as a neural correlate of patients' rhythm propensity and fondness of music. Similar sizes of the auditory cortex have been previously reported only in professional musicians.
Cognitively, global Intelligence Quotient scores of individuals with Williams syndrome vary widely, but are often low. One study of 306 children with Williams syndrome found IQ scores ranging from 40 to 112 with a mean of 69.32 (an IQ score of 100 is the average in nonaffected populations).
Despite their physical and cognitive deficits, individuals with Williams syndrome exhibit impressive social and verbal abilities. Williams patients can be highly verbal relative to their IQ. When children with Williams syndrome are asked to name an array of animals, they may well list such a wild assortment of creatures as a koala, saber-toothed tiger, vulture, unicorn, sea lion, yak, ibex and "Brontosaurus", a far greater verbal array than would be expected of children with IQs in the 60s.
Some other strengths that have been associated with Williams Syndrome are auditory short-term memory and facial recognition skills.