[2] Facial features frequently include a broad forehead, underdeveloped chin, short nose, and full cheeks.
[2][4] Medical issues with teeth, heart problems (especially supravalvular aortic stenosis), and periods of high blood calcium are common.
[1][2] Williams syndrome is caused by a genetic abnormality, specifically a deletion of about 27 genes from the long arm of one of the two chromosome 7s.
[10] People with Williams syndrome experience many cardiac problems, commonly heart murmurs and the narrowing of major blood vessels, as well as supravalvular aortic stenosis.
[14] People with WS often have hyperacusia and phonophobia, which resembles noise-induced hearing loss; however, this may be due to a malfunctioning auditory nerve.
Up to 75% of subjects in some studies have strabismus (ocular misalignment), particularly esotropia,[19] due to inherent subnormal binocular visual function[20] and cognitive deficits in visuospatial construction.
[21] People with WS have problems with visual processing, but this is related to difficulty in dealing with complex spatial relationships rather than depth perception per se.
[22] Because of missing multiple genes, many effects on the brain are seen, including abnormalities in the cerebellum, right parietal lobe, and left frontal cortical regions.
[citation needed] Frontal-cerebellar pathways, involved in behavioral timing, are often abnormally developed in people with WS, which may be related to their deficits in coordination and execution of fine motor tasks such as drawing and writing.
[28] Increased volume and activation of the left auditory cortex has been observed in people with WS, which has been interpreted as a neural correlation of patients' rhythm propensity and fondness of music.
[29] The earliest observable symptoms of Williams syndrome include low birth weight, failure to thrive, breastfeeding difficulties, nocturnal irritability, and gastroesophageal reflux.
Research on the development of the syndrome suggests that congenital heart disease is typically present at an early age, often at the infant's first pediatric appointment.
[31] Adults and adolescents with Williams syndrome typically achieve a below-average height and weight, compared with unaffected populations.
As people with WS age, they frequently develop joint limitations and hypertonia, or abnormally increased muscle tone.
Adults are typically limited in their ability to live independently or work in competitive employment settings, but this developmental impairment is attributed more to psychological symptoms than physiological problems.
[32] People with Williams syndrome report higher anxiety levels as well as phobia development, which may be associated with hyperacusis (high sensitivity to certain frequencies of sound).
[9] Furthermore, cognitive abilities (IQs) of people with WMS typically range from mild to moderate levels of intellectual disability.
Most affected people are unable to spatially orient themselves and many experience difficulty when given a task that requires even the most basic visual problem-solving.
Dykens and Rosner (1999) found that 100% of those with Williams syndrome were kind-spirited, 90% sought the company of others, 87% empathize with others' pain, 84% are caring, 83% are unselfish/forgiving, 75% never go unnoticed in a group, and 75% are happy when others do well.
This is possibly due to the fact that although they are very friendly to strangers and love meeting new people, they may have trouble interacting on a deeper level.
73–93% were reported as unreserved with strangers, 67% highly sensitive to rejection, 65% susceptible to teasing, and the statistic for exploitation and abuse was unavailable.
Elastin insufficiency may also contribute to distinct facies, harsh or hoarse voice, hernias, and bladder diverticula often found in those with Williams syndrome.
Additionally, some evidence shows that haploinsufficiency in several of these genes, including CLIP2, may contribute to the unique behavioral characteristics, learning disabilities, and other cognitive difficulties seen in WS.
[51] According to the Williams Syndrome Association, its diagnosis begins with the recognition of physical symptoms and markers, which is followed by a confirmatory genetic test.
The physical signs that often indicate a suspected case of WS include puffiness around the eyes, a long philtrum, and a stellate pattern in the iris.
Physiological symptoms that often contribute to a WS diagnosis are cardiovascular problems, particularly aortic or pulmonary stenosis, and feeding disturbance in infants.
Among the more reliable features suggestive of WS are congenital heart disease, periorbital fullness ("puffy" eyes), and the presence of a long, smooth philtrum.
Even with significant clinical experience, reliably identifying Williams syndrome based on facial features alone is difficult.
As increasing evidence suggests WS is more common than originally noted (about 6% of all genetic cases of developmental disability), researchers have begun to hypothesize a previous underdiagnosis of the syndrome.
Then in 1975, K. Jones and D. Smith produced a large-scale report on numerous patients with WS, ranging in age from infancy to adulthood, and described the behavioral and observable physical symptoms in greater detail than previously recorded.