Williams syndrome

Synonyms

3

Overview

Williams syndrome (WS, also known as Williams–Beuren syndrome,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; profound visuo-spatial impairments; and cardiovascular problems, such as supravalvular aortic stenosis and transient high blood calcium.

It is caused by a deletion of about 26 genes from the long arm of chromosome 7. It occurs in 1 in 7,500 to 1 in 20,000 births. The syndrome was first identified in 1961 by New Zealander J.C.P. Williams.

Symptoms

The most common symptoms of Williams syndrome are heart defects, and unusual facial features. Other symptoms include failure to gain weight appropriately in infancy (failure to thrive) and low muscle tone. Individuals with Williams syndrome tend to have widely spaced teeth, a long philtrum, and a flattened nasal bridge.

Most individuals with Williams syndrome are highly verbal relative to their IQ, and are overly sociable, having what has been described as a "cocktail party" type personality. Individuals with WS hyperfocus on the eyes of others in social engagements.

It is in some respects the opposite of autism; individuals with WS are more sociable than those with autism, but those with WS have impairment in cognitive function as it relates to visuospatial functioning.

Physical

Individuals with Williams syndrome experience many cardiac problems, commonly heart murmurs and the narrowing of major blood vessels as well as supravalvular aortic stenosis. Other symptoms may include gastrointestinal problems, such as severe or prolonged colic, abdominal pain and diverticulitis, nocturnal enuresis (bed wetting) and urinary difficulties, dental irregularities and defective tooth enamel, as well as hormone problems, the most common being high blood calcium. Hypothyroidism has been reported to occur in children, although there is no proof of it occurring in adults; adults with WS have a higher risk of developing diabetes, with some cases apparent as young as 21 years old.

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. Individuals with Williams syndrome have problems with visual processing, but this is related to difficulty in dealing with complex spatial relationships rather than depth perception per se.

Nervous system

Because of the multiple genes that are missing in people with Williams syndrome, there are many effects on the brain, including abnormalities in the cerebellum, right parietal cortex, and left frontal cortical regions. This pattern is consistent with the visual-spatial disabilities and problems with behavioral timing often seen in Williams syndrome.

Frontal-cerebellar pathways, involved in behavioral timing, are often abnormally developed in individuals with Williams syndrome, which may be related to their deficits in coordination and execution of fine motor tasks such as drawing and writing. 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).

Williams syndrome is also noteworthy for exhibiting abnormalities in the parietal-dorsal areas of the neocortex, but not the ventral areas. The parietal-dorsal area handles visual processing that supports visual-spatial analysis of the environment, while the ventral is related to semantic recognition of visual stimuli, as well as the recognition of faces. Thus, individuals with Williams syndrome are often able to visually identify and recognize whole objects, and refer to them by name, but struggle with visuospatial construction (seeing an object as being composed of many smaller parts, and recreating it) and orienting themselves in space.

People with Williams syndrome are often affable and hyperverbal, demonstrating the decreased inhibition ability that stems from dorsal-frontal deficits. Some studies suggest that the amygdala of a person with Williams syndrome has greater volume than the average person's (though it is smaller than average in childhood). In general, neuroimaging studies demonstrate that individuals with Williams syndrome have diminished amygdala reactivity in response to socially frightening stimuli (such as disapproving faces), but demonstrate hyperreactivity in the amygdala when presented with nonsocial fear stimuli (such as frightening animals). This may partially account for the apparent absence of social inhibition observed in individuals with the syndrome, as well as the prevalence of anxious symptoms (but see fear for details on the relationship between the amygdala and fear response). There is also evidence that individuals with Williams exhibit hyper amygdala activity when viewing happy facial expressions.

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.

Developmental

The earliest observable symptoms of Williams syndrome include low birth weight, failure to thrive, trouble breastfeeding, nocturnal irritability and gastroesophageal reflux. Facial dysmorphies thought to be characteristic of the syndrome are also present early in development, as is heart murmur. Research on the development of the syndrome suggest that congenital heart disease is typically present at an early age, often at the infant's first pediatric appointment. Heart problems in infancy often lead to the initial diagnosis of Williams syndrome.

Developmental delays are present in most cases of Williams syndrome, and include delay of language abilities and delayed motor skill development. Individuals with Williams syndrome develop language abilities quite late relative to other children, with the child's first word often occurring as late as three years of age. Language abilities are often observed to be deficient until adolescence, in terms of semantics,morphology, and phonology, though not in vocabulary.

Williams syndrome is also marked by a delay in development of motor skills. Infants with Williams develop the ability to lift their heads and sit without support months later than typically developing children. These delays continue into childhood, where patients with Williams syndrome are delayed in learning to walk. In young children, the observed motor delay is around five to six months, though some research suggests that children with Williams syndrome have a delay in development that becomes more extreme with age. Children with motor delays as a result of Williams syndrome are particularly behind in development of coordination, fine motor skills such as writing and drawing, response time, and strength and dexterity of the arms. Impaired motor ability persists (and possibly worsens) as children with Williams syndrome reach adolescence.

Adults and adolescents with Williams syndrome typically achieve a below-average height and weight, compared with non-affected populations. As individuals with Williams syndrome age, they frequently develop joint limitations and hypertonia, or abnormally increased muscle tone. Hypertension, gastrointestinal problems, and genitourinary symptoms often persist into adulthood, as well as cardiovascular problems. Adults with Williams syndrome 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.

Social and psychological

Individuals 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). Compared with other children with delays, those with Williams syndrome show a significantly greater amount of fears. Some of those often seen are falling from high places, arguments between others, mean dogs, bee stings and thunderstorms. 35% of these children met the DSM definition of having a phobia as compared with 1-4.3% for those with other types of developmental delays. Williams syndrome is also strongly associated with attention deficit hyperactivity disorder and related psychological symptoms such as poor concentration, hyperactivity, and social disinhibition.

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). IQ scores above this range have been reported in individuals with smaller genetic deletions. In particular, individuals with Williams syndrome experience challenges in visual-motor skills and visuospatial construction. Most affected individuals are unable to spatially orient themselves and many experience difficulty when given a task that requires even the most basic visual problem solving. Many adults with Williams syndrome cannot complete a simple six-piece puzzle designed for young children, for example. These visuospatial deficits may be related to damage to the dorsal cortical pathway for visual processing.

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 cat, 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. The language used by individuals with Williams syndrome differs notably from unaffected populations, including individuals matched for IQ. People with Williams syndrome tend to use speech that is rich in emotional descriptors, high in prosody (exaggerated rhythm and emotional intensity), and features unusual terms and strange idioms.

Among the hallmark traits of individuals with Williams syndrome is an apparent lack of social inhibition. Dykens and Rosner (1999) found that 100% of those with Williams syndrome were kindred-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. Infants with Williams syndrome make normal and frequent eye contact, and young children with Williams will often approach and hug strangers. Individuals affected by Williams syndrome typically have high empathy, and are rarely observed displaying aggression. In regards to empathy, they show relative strength in reading people's eyes to gauge intentions, emotions, and mental states. The level of friendliness observed in people with Williams is often inappropriate for the social setting, however, and teens and adults with Williams syndrome often experience social isolation, frustration, and loneliness despite their clear desire to connect to other people.

While these children often came off as happy due to their sociable nature, often there are internal drawbacks to the way they act. 76-86% of these children were reported as believing that they either had few friends or problems with their friends. 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. This last one is a significant problem. People with Williams syndrome are frequently very trusting and want more than anything to make friends, leading them to submit to requests that under normal circumstances would be rejected. There are external problems as well. 91-96% demonstrate inattention, 75% impulsivity, 59-71% hyperactivity 46-74% tantrums, 32-60% disobedience, and 25-37% fighting and aggressive behavior.

In one experiment, a group of children with Williams syndrome showed no signs of racial bias, unlike children without the syndrome. They did show gender bias, however, suggesting separate mechanisms for these biases.

Causes

Williams syndrome is a microdeletion syndrome caused by the spontaneous deletion of genetic material from the region q11.23 of chromosome 7. The deleted region includes more than 25 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 and supravalvular pulmonary stenosis) found in many people with this syndrome. The insufficient supply of elastin may also be the cause of full cheeks, coarse voice, hernias and bladder diverticulae often found in those with Williams 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.

Diagnosis

According to the Williams Syndrome Association, diagnosis of Williams syndrome begins with recognition of physical symptoms and markers, which is followed by a confirmatory genetic test. The physical signs that often indicate a suspected case of Williams syndrome include puffiness around the eyes, a long philtrum, and a stellate pattern in the iris. Physiological symptoms that often contribute to a Williams syndrome diagnosis are cardiovascular problems, particularly aortic or pulmonary stenosis, as well as feeding disturbance in infants. Developmental delays are often taken as an initial sign of the disorder, as well.

If a physician suspects a case of Williams syndrome, the diagnosis is confirmed using one of two possible genetic tests: micro-array analysis or the fluorescent in situ hybridization (FISH) test. The FISH test examines chromosome #7 and probes for the existence of two copies of the elastin gene. Since 98-99% of individuals with Williams syndrome lack half of the 7q11.23 region of chromosome #7, where the elastin gene is located, the presence of only one copy of the gene is a strong sign of the disorder. This confirmatory genetic test has been validated in epidemiological studies of the disorder, and has been demonstrated to be a more effective method of identifying Williams syndrome than previous methods, which often relied on the presence of cardiovascular problems and facial features (which, while common, are not always present).

Some diagnostic studies suggest that reliance on facial features to identify Williams syndrome may cause a misdiagnosis of the condition. Among the more reliable features suggestive of Williams are congenital heart disease, periorbital fullness ("puffy" eyes), and the presence of a long smooth philtrum. Less reliable signs of the syndrome include anteverted nostrils, a wide mouth, and an elongated neck. Researchers indicate that even with significant clinical experience, it is difficult to reliably identify Williams syndrome based on facial features alone.

Treatment

There is no cure for Williams syndrome. Suggestions include avoidance of extra calcium and vitamin D, as well as treating high levels of blood calcium. Blood vessel narrowing can be a significant health problem, and is treated on an individual basis. Physical therapy is helpful to patients with joint stiffness and low muscle tone. Developmental and speech therapy can also help children and increase the success of their social interactions. Other treatments are based on a patient's particular symptoms.

The American Academy of Pediatrics recommends annual cardiology evaluations for individuals with Williams syndrome. Other recommended assessments include: ophthalmologic evaluations, an examination for inguinal hernia, objective hearing assessment, blood pressure measurement, developmental and growth evaluation, orthopedic assessments on joints, muscle tone, and ongoing feeding and dietary assessments to manage constipation and urinary problems.

Behavioral treatments have been shown to be effective. In regards to social skills it may be effective to channel their nature by teaching basic skills. Some of these are the appropriate way to approach someone, how and when to socialize in settings such as school or the workplace, and warning of the signs and dangers of exploitation. For the fear that they demonstrate cognitive-behavioral approaches, such as therapy, are the recommended treatment. One of the things to be careful of with this approach is to make sure that the patients' charming nature does not mask any underlying feelings.

Perhaps the most effective treatment for those with Williams syndrome is music. Those with Williams syndrome have shown a relative strength in regards to music, albeit only in pitch and rhythm tasks. Not only do they show a strength in the field but also a particular fondness for it. It has been shown that music may help with the internal and external anxiety that these people are more likely to be afflicted with. Something of note is that the typical person processes music in the superior temporal and middle temporal gyri. Those with Williams syndrome have a reduced activation in these areas but an increase in the right amygdala and cerebellum.

People affected by Williams syndrome are supported by multiple organizations, including the Canadian Association for Williams Syndrome and the Williams Syndrome Registry.