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Williams Syndrome

Williams syndrome

Definition

A rare congenital (present from birth) genetic disorder that results in physical and developmental delays and problems.

Description

Williams syndrome (WS) is sometimes also referred to as Williams-Beuren syndrome. The disorder was first described by J. C. P. Williams of New Zealand in 1961. WS is a genetic disorder that can be inherited but often arises through spontaneous change in a chromosome (mutation). Children with WS usually have a variety of physical problems, especially problems with hearts defects. They have "elfin" faces and usually are of short stature. Children with WS are often overfriendly and have varying intellectual disabilities, with relatively good skills in music and language.

Demographics

WS is estimated to occur in about one in 20,000 births. It affects about the same number of boys and girls.

Causes and symptoms

WS is thought to be caused by a deletion of genetic information on chromosome 7. WS can be passed down from parent to child, but it often arises spontaneously. The way in which WS spontaneously arises is not clear.

Physical characteristics typical of Williams syndrome include a broad forehead, puffiness around the eyes, starburst eye pattern (usually in green or blue-eyed children), upturned nose, depressed nasal bridge, full lips, widely spaced teeth, and small chin. In addition, a child with Williams syndrome often exhibits sloping shoulders or an elongated neck. Many individuals with Williams syndrome have heart disorders, typically supravalvular aortic stenosis (SVAS), which is a narrowing of the aorta. Kidney and bladder problems are also common. Poor muscle tone and problems with the skeletal joints become evident as a child with Williams syndrome moves into adolescence . As the child gets older hypertension often becomes a problem.

Williams syndrome babies typically have a low birth weight and are often diagnosed as failing to thrive. Elevated levels of calcium in the blood (hypercalcemia) may develop in infancy, but this usually resolves without intervention in the first two years. Digestive system symptoms such as vomiting , constipation , and feeding difficulties may occur. The infant may not be able to settle into a normal sleep pattern and may seem to be extremely sensitive to noise, exhibiting agitation or distress when exposed to high-pitched sounds, such as electrical appliances, motors, and loud bangs.

By the time a child with Williams syndrome is ready to enter school, mild to severe learning difficulties may appear, including impulsiveness and poor concentration. Contributing to classroom difficulties are problems with vision and spatial relations. Concepts involving numbersespecially math and timeappear to be more difficult for children with WS. In the later elementary school years, a child with Williams syndrome may be more adept at producing language than at comprehending it. Poor muscle tone and physical development continue to contribute to difficulties with gross and fine motor skills . The child with WS may have difficulty forming relationships with peers, preferring the company of younger children or adults. Throughout childhood, the child with Williams syndrome may exhibit deficits in the ability to reason and in self-help skills.

Children with WS are overly social and outgoing, inappropriately friendly to adults and unwary of strangers. They are usually talkative, with intense enthusiasm bordering on obsession for topics that interest them.

Special care needs to be taken when children with Williams syndrome are given anesthesia.

When to call the doctor

If a parent notices that a child has the symptoms of WS the doctor should be consulted.

Diagnosis

Williams syndrome is present from birth, although it often remains undiagnosed until a later stage of development. After a child has missed several developmental milestones, the pediatrician may refer the child to a specialist for diagnosis. Developmental delays that are typical include delay in sitting or walking. Also commonly observed are poor fine motor coordination and delayed development in language (although individuals with WS go on to develop excellent language skills). After reviewing the child's medical and family history, physical condition, and observing the child's behavior, a specialist in birth defects may identify Williams syndrome. In many cases, a heart murmur or suspected heart disorder may lead a cardiologist to suspect Williams syndrome, since an estimated 70 to 75 percent of people with WS have mild to severe cardiovascular problems.

Until the early 2000s, the diagnosis of WS made based on the child having a certain number of the symptoms of the disease. As of 2004, it was possible to test a child's genes for the deletion that causes WS. A test technique known as fluorescent in situ hybridization (FISH) may be used to detect this deletion. This test is only done when it is considered very likely that a child has WS because many of the clinical features are present.

Treatment

Williams syndrome cannot be cured, but the ensuing symptoms, developmental delays, learning problems, and behaviors can be treated. Many different experts work together to help develop a comprehensive treatment plan that is geared to the needs of a specific child. Children need to be monitored regularly by a doctor to ensure that problems, especially cardiac problems and hypertension, do not arise. If such problems do arise, they need to be treated promptly. Non-physical treatment often involves teaching children life skills that will eventually allow them to live on their own or with minimal care and to hold jobs. Specialists who can be helpful in treating Williams syndrome include the following:

  • cardiologist, to diagnose and prescribe treatment for heart or circulatory problems
  • endocrinologist, to prescribe treatment if elevated calcium levels are detected in infancy
  • pediatric radiologist, to conduct diagnostic renal and bladder ultrasound tests to diagnose and prescribe treatment for any abnormalities present
  • occupational therapist, to assess development delays and prescribe a plan for therapy to acquire skills necessary for daily living

Prognosis

In most cases, the child with WS will require multidisciplinary care throughout adult life, with continued medical assessment to diagnose and treat medical complications early. The ability to live independently and to work are usually not limited by the physical problems, which are treated successfully in the majority of cases. Rather, psychological characteristics and the inability to behave appropriately in social settings are more likely to prevent the individual from living and functioning completely on his or her own. However, each year more individuals with William syndrome are able to live independently in supervised apartment settings.

Prevention

There was as of 2004 no known way to prevent Williams syndrome.

Parental concerns

Children with Williams syndrome usually grow up physically healthy as long as they receive treatment for any problems, especially cardiac problems, that arise. The amount of independence that a child with Williams syndrome will eventually be able to achieve usually depends on the particular symptoms of that child.

KEY TERMS

Fluorescence in situ hybridization (FISH) A technique for diagnosing genetic disorders before birth by analyzing cells obtained by amniocentesis with DNA probes.

Hypercalcemia A condition marked by abnormally high levels of calcium in the blood.

Supravalvular aortic stenosis (SVAS) A narrowing of the aorta.

Resources

BOOKS

Bellugi, Ursula, and Marie St. George, eds. Journey from Cognition to Brain to Gene: Perspectives from Williams Syndrome. Cambridge, MA: MIT Press, 2001.

Schiber, Barbara. Fulfilling Dreams: A Handbook for Parents of Children with Williams Syndrome. Clawson, MI: Williams Syndrome Association, 2000.

Semel, Eleanor, and Sue R. Rosner. Understanding Williams Syndrome: Behavioral Patterns and Interventions. Mahwah, NJ: L. Erlbaum, 2003.

PERIODICALS

Jason, Helen, et al. "Word Reading and Reading-Related Skills in Adolescents With Williams Syndrome." Journal of Child Psychology and Psychiatry and Allied Disciplines 44 (May 2003): 57687.

Reis, Sally M., et al. "Minds Music: Using a Talent Development Approach for Young Adults with Williams Syndrome." Exceptional Children 69 (Spring 2003): 293314.

ORGANIZATIONS

Williams Syndrome Association. PO Box 297 Clawson, MI 480170297. Web site: <www.williams-syndrome.org>.

Williams Syndrome Foundation. Williams Syndrome Foundation, University of California, Irvine, CA 926972300. Web site: <www.wsf.org>

Tish Davidson, A.M.

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Williams Syndrome

Williams syndrome

Definition

Williams syndrome, first described in 1961, is a rare genetic condition with a wide array of clinical features.

Description

Typical facial features seen in children with Williams syndrome include a wide mouth with full lips, a small chin, and a short, slightly upturned nose. Children with blue or green eyes often times show a starburst pattern in the colored part (iris) of the eyes. An unusual narrowing of the aorta called supravalvular aortic stenosis is often present, and hernias are often seen in the inguinal area of the abdomen. The blood vessels and abdominal wall often show weakness or altered development. Muscle tone is typically low, and children are often on the low end of birth weight, with relatively poor weight gain and growth in their early years.

Most children with Williams syndrome have a remarkable contrast between verbal abilities and spatial abilities. While overall intellectual performance on standardized IQ tests will be in the general range found in Down syndrome, children with Williams syndrome show a complex pattern of strengths and deficiencies that would not be evident by counting IQ points. Verbal abilities, for example, are exceptionally strong, and people with Williams syndrome tend to show very strong social skills relative to what one might anticipate based on IQ scores. Long-term memory is also generally excellent. Musical interest and ability are often strong. In contrast, fine motor skills often lag behind their IQ-matched peers, and, the sense of spatial relationships is very poor. If a therapist, for example, were to ask a child with Williams syndrome for a picture of a boy on a bike, the child might not be able to identify many of the parts of the picture. The parts will not likely be spaced in a way that makes much sense. However, if the therapist asks for a description of what it is like to ride a bike, the child will likely describe the sensation with a detailed and imaginative story.

For reasons that are not well understood, children may have a problem with calcium levels that are too high. Irritability and colic are common in early development, especially in children with high calcium levels. Delays are typically seen in reaching developmental milestones, and children with Williams syndrome generally exhibit learning disabilities and may be easily distractible with some form of attention deficit disorder. Cognitive, verbal and motor deficits are universal, and about three quarters of children will be determined to have mental retardation in the course of their care.Young children with Williams syndrome often have extremely sensitive hearing, although this tends to become less significant as children get older.

Demographics

Williams syndrome is estimated to occur in one of every 20,000 births. In most families, only one child will be affected and there is no significant family history of Williams syndrome in other relatives.

Causes and symptoms

Williams syndrome is most often caused by a chromosome deletion involving loss of a gene called elastin on chromosome number 7, and may involve the loss of other neighboring genes as well.

Diagnosis

Because of the variability in the way that Williams syndrome affects different people, it often goes undiagnosed for many years. Although there is a chromosome deletion in over 98% of children born with Williams syndrome, the deletions are so small that they are usually not detectable under the microscope using standard methods. Diagnosis requires the use of a special test called fluorescence in situ hybridization (FISH) in which a DNA probe for the elastin gene is labeled with a brightly colored fluorescent dye.

Treatment team

Medical care for children with Williams syndrome should be provided by a physician with specific knowledge or experience with Williams syndrome, and growth charts specific to children with Williams syndrome are available. The services of a medical geneticist should be available to the treating physician.

Treatment

Treatment is supportive and varies according to the symptoms displayed. Special attention is given to monitoring for heart and blood vessel disease, along with blood calcium levels. Multivitamin supplementation should generally be avoided unless directed by a physician because of the potential for problems caused by vitamin D.

Recovery and rehabilitation

Teens and adults with Williams syndrome face a variety of challenges that come with aging. Involvement of the family in support groups with other families that have direct experience with Williams syndrome can be helpful in anticipating and avoiding the common pitfalls. Most adults with Williams syndrome continue to live at home with parents or in special group home situations, with rare individuals living and functioning independently.

Prognosis

There is no cure for Williams syndrome as it is a genetically determined disease. Research is underway to determine the roles of approximately 20 genes in the area of chromosome 7 that are critical to the development of Williams syndrome.

Special concerns

Individuals who have Williams syndrome have a 50% chance of passing it on to their offspring if they have children because one of their two copies of chromosome 7 is missing some vital information, and each sperm or egg will receive one copy of chromosome 7 at random. This inheritance pattern is called autosomal pseudodominant because it so closely resembles the pattern of transmission seen for autosomal dominant single gene traits.

Resources

BOOKS

Semel, Eleanor, and Sue R. Rosner. Understanding Williams Syndrome: Behavioral Patterns and Interventions. Mahwah, NJ: Lawrence Erlbaum Assoc, 2003.

PERIODICALS

Committee on Genetics American Academy of Pediatrics. "Health care supervision for children with Williams syndrome." Pediatrics 107 (2001): 11921204.

OTHER

"NINDS Williams Syndrome Information Page." National Institute of Neurological Disorders and Stroke. (February 11, 2004). <http://www.ninds.nih.gov/health_and_medical/disorders/williams.htm#Is_there_any_treatment>.

ORGANIZATIONS

Williams Syndrome Association. P.O. Box 297, Clawson, MI 48017-0297. (248) 244-2229 or (800) 806-1871; Fax: (248) 244-2230. [email protected] <http://www.williams-syndrome.org>.

National Organization for Rare Disorders (NORD), P.O. Box 1968 (55 Kenosia Avenue), Danbury, CT 06813-1968. (203) 744-0100 or (800) 999-NORD (6673); Fax: (203) 798-2291. [email protected], <http://www.rarediseases.org>.

Robert G. Best, PhD

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Williams syndrome

Williams syndrome (wil-yămz) n. a hereditary condition marked by a characteristic ‘elfin’ facial appearance, hypercalcaemia, short stature, mental retardation, and aortic stenosis. Most affected children are highly sociable and have unusual conversational ability, using a rich and complex vocabulary. [ J. C. P. Williams (20th century), British cardiologist]

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Williams syndrome

Williams syndrome

Definition

Williams syndrome is a genetic disorder caused by a deletion of a series of genes on chromosome 7q11. Individuals with Williams syndrome have distinctive facial features, mild mental retardation, heart and blood vessel problems, short stature, unique personality traits, and distinct learning abilities and deficits.

Description

Williams syndrome, also known as Williams Beuren syndrome, was first described in 1961 by Dr. J.C.P. Williams of New Zealand. At that time it was noted that individuals with Williams syndrome had an unusual constellation of physical and mental findings. The physical features include a characteristic facial appearance, heart and cardiovascular problems, high blood calcium levels, low birth weight, short stature, and other connective tissue abnormalities. The intellectual problems associated with Williams include a mild mental retardation and a specific cognitive profile. That is, individuals with Williams syndrome often have the same pattern of learning abilities and disabilities, as well as many similar personality traits.

The findings in Williams syndrome are variable—that is, not all individuals with Williams syndrome will have all of the described findings. In addition to being variable, the physical and mental findings associated with Williams syndrome are progressive—they change over time.

Genetic profile

Williams syndrome is a genetic disorder due to a deletion of chromosome material on the long arm of chromosome 7. A series of genes are located in this region. Individuals with Williams syndrome may have some or all of these genes deleted. Because of this, Williams syndrome is referred to as a contiguous gene deletion syndrome. Contiguous refers to the fact that these genes are arranged next to each other. The size of the deletion can be large or small, which may explain why some individuals with Williams syndrome are more severely affected than others. If you think of these genes as the letters of the alphabet, some individuals with Williams syndrome are missing A to M, some are missing G to Q and others are missing A to R. While there are differences in the amount of genetic material that can be deleted, there is a region of overlap. Everyone in the above example was missing G to M. It is thought that the missing genes in this region are important causes of the physical and mental findings of Williams syndrome.

Two genes in particular, ELN and LIMK1, have been shown to be important in causing some of the characteristic symptoms of Williams syndrome. The ELN gene codes for a protein called elastin. The job of elastin in the human body is to provide elasticity to the connective tissues such as those in the arteries, joints, and tendons. The exact role of the LIMK1 gene is not known. The gene codes for a substance known as lim kinase 1 that is active in the brain. It is thought that the deletion of the LIMK1 gene may be responsible for the visuospatial learning difficulties of individuals with Williams syndrome. Many other genes are known to be in the deleted region of chromosome 7q11 responsible for Williams syndrome and much work is being done to determine the role of these genes in Williams syndrome.

Williams syndrome is an autosomal dominant disorder. Genes always come in pairs and in an autosomal dominant disorder, only one gene need be missing or altered for an individual to have the disorder. Although Williams syndrome is an autosomal disorder, most individuals with Williams syndrome are the only people in their family with this disorder. When this is the case, the chromosome deletion that causes Williams syndrome is called de novo. A de novo deletion is one that occurs for the first time in the affected individual. The cause of de novo chromosome deletions is unknown. Parents of an individual with Williams syndrome due to a de novo deletion are very unlikely to have a second child with William syndrome. However, once an individual has a chromosome deletion, there is a 50% chance that he or she will pass it on to their offspring. Thus individuals with Williams syndrome have a 50% chance of passing this deletion (and Williams syndrome) to their children.

Demographics

Williams syndrome occurs in 1 in 20,000 births. Because Williams syndrome is an autosomal dominant disorder, it affects an equal number of males and females. It is thought that Williams syndrome occurs in people of all ethnic backgrounds equally.

Signs and symptoms

Williams syndrome is a multi-system disorder. In addition to distinct facial features, individuals with Williams syndrome can have cardiovascular, growth, joint, and other physical problems. They also share unique personality traits and have intellectual differences.

Infants with Williams syndrome are often born small for their family and 70% are diagnosed with failure to thrive during infancy. These growth problems continue throughout the life of a person with Williams syndrome and most individuals with Williams syndrome have short stature (height below the third percentile). Infants with William syndrome can also be extremely irritable and have "colic-like" behavior. This behavior is thought to be due to excess calcium in the blood (hypercalcemia). Other problems that can occur in the first years include strabismus (crossed eyes), ear infections, chronic constipation, and eating problems.

Individuals with Williams syndrome can have distinct facial features sometimes described as "elfin" or "pixie-like." While none of these individual facial features are abnormal, the combination of the different features is common for Williams syndrome. Individuals with Williams syndrome have a small upturned nose, a small chin, long upper lip with a wide mouth, small widely spaced teeth, and puffiness around the eyes. As an individual gets older, these facial features become more pronounced.

People with Williams syndrome often have problems with narrowing of their heart and blood vessels. This is thought to be due to the deletion of the elastin gene and is called elastin arteriopathy. Any artery in the body can be affected, but the most common narrowing is seen in the aorta of the heart. This condition is called supravalvar aortic stenosis (SVAS) and occurs in approximately 75% of individuals with Williams syndrome. The degree of narrowing is variable. If left untreated, it can lead to high blood pressure, heart disease, and heart failure. The blood vessels that lead to the kidney and other organs can also be affected.

Deletions of the elastin gene are also thought to be responsible for the loose joints of some children with Williams syndrome. As individuals with Williams syndrome age, their heel cords and hamstrings tend to tighten, which can lead to a stiff awkward gait and curving of the spine.

Approximately 75% of individuals with Williams syndrome have mild mental retardation. They also have a unique cognitive profile (unique learning abilities and disabilities). This cognitive profile is independent of their IQ. Individuals with Williams syndrome generally have excellent language and memorization skills. They can have extensive vocabularies and may develop a thorough knowledge of a topic that they are interested in. Many individuals are also gifted musicians. Individuals with Williams syndrome have trouble with concepts that rely on visuospatial ability. Because of this, many people with Williams syndrome have trouble with math, writing and drawing.

People with Williams syndrome also often share personality characteristics. They are noted to be very talkative and friendly—sometimes inappropriately—and they can be hyperactive. Another shared personality trait is a generalized anxiety.

Diagnosis

The diagnosis of Williams syndrome is usually made by a physician familiar with Williams syndrome and based upon a physical examination of the individual and a review of his or her medical history. It is often made in infants after a heart problem (usually SVAS) is diagnosed. In children without significant heart problems, the diagnosis may be made after enrollment in school when they are noted to be "slow learners."

While a diagnosis can be made based upon physical examination and medical history, the diagnosis can now be confirmed by a DNA test.

Williams syndrome is caused by a deletion of genetic material from the long arm of chromosome 7. A specific technique called fluorescent in situ hybridization testing, or FISH testing, can determine whether there is genetic material missing. A FISH test will be positive (detect a deletion) in over 99% of individuals with Williams syndrome. A negative FISH test for Williams syndrome means that no genetic material is missing from the critical region on chromosome 7q11.

Prenatal testing (testing during pregnancy) for Williams syndrome is possible using the FISH test on DNA sample obtained by chorionic villus sampling (CVS) or by amniocentesis . Chorionic villus sampling is a prenatal test that is usually done between 10 and 12 weeks of pregnancy and involves removing a small amount of tissue from the placenta. Amniocentesis is a prenatal test that is usually performed at 16–18 weeks of pregnancy and involves removing a small amount of the amniotic fluid that surrounds the fetus. DNA is obtained from these samples and tested to see if the deletion responsible for Williams syndrome is present. While prenatal testing is possible, it is not routinely performed. Typically, the test is only done if there is a family history of Williams syndrome.

Treatment and management

Because Williams syndrome is a multi-system disorder, the expertise of a number of specialists is required for management of this disorder.

The height and growth of individuals with Williams syndrome should be monitored using special growth curves developed specifically for individuals with Williams syndrome. Individuals who fall off these growth curves should be worked up for possible eating or thyroid disorders.

A cardiologist should evaluate individuals with Williams syndrome yearly. This examination should include measurement of blood pressure in all four limbs and an echocardiogram of the heart. An echocardiogram is a special form of ultrasound that looks at the structure of the heart. Doppler flow studies, which look at how the blood flows into and out of the heart, should also be done. Individuals with supravalvar stenosis may require surgery to fix this condition. The high blood pressure caused by this condition may be treated with medication. Examinations should take place yearly as some of these conditions are progressive and may worsen over time.

Individuals with Williams syndrome should also have a complete neurological examination. In addition, the blood calcium levels of individuals with Williams syndrome should be monitored every two years. High levels of calcium can cause irritability, vomiting, constipations and muscle cramps. An individual found to have a high level of calcium should consult a nutritionist to make sure that their intake of calcium is not higher than 100% of the recommended daily allowance (RDA). Because vitamin D can increase calcium levels, individuals with Williams syndrome and high calcium should not take multivitamins containing vitamin D. If calcium levels remain high after limiting vitamin D and decreasing dietary intake of calcium, an individual with hypercalcemia should see a nephrologist for further management and to monitor kidney function.

Strabismus (crossed eyes) can be treated by patching or by surgery. Ear infections can be treated with antibiotics and surgical placement of ear tubes.

The developmental differences of individuals with Williams syndrome should be treated with early intervention and special education classes. Specific learning strategies that capitalize on the strengths of individuals with Williams syndrome should be used. Physical, occupational, and speech therapy should be provided. Behavioral counseling and medication may help with behavioral problems such as hyperactivity and anxiety.

Prognosis

The prognosis for individuals with Williams syndrome is highly dependent on the medical complications of a particular individual. Individuals with Williams syndrome who have no heart complications, or very minor ones, have a good prognosis. Good medical care and treatment of potential problems allows most individuals with Williams syndrome to lead a long life. The prognosis for individuals with more serious medical complications such as severe heart disease or hypertension is more guarded. Since the medical conditions associated with Williams syndrome are progressive rather than static, it is very important that individuals with Williams syndrome have yearly medical examinations with a health care provider familiar with Williams syndrome.

The range of abilities among individuals with Williams syndrome is very wide and the ultimate functioning of an individual is dependent on his or her abilities. While individuals with Williams syndrome do well in structured environments such as school, their unique abilities and disabilities do not permit them to do as well in unstructured surroundings. Some individuals with Williams syndrome live independently but most live with their parents or in a supervised setting. Many individuals with Williams syndrome can gain employment in supervised settings and do well at tasks that do not require mathematics or visuospatial abilities. It is important to encourage individuals with Williams syndrome towards independence but to recognize that their friendly and outgoing personalities may lead them into abusive situations.

Resources

BOOKS

Bellugi, Ursula, and Marie St. George. Journey from Cognition to Brain to Gene: Perspectives from Williams Syndrome. Cambridge, MA: MIT Press, 2001.

PERIODICALS

Finn, Robert. "Different Minds." Discover (June 1991): 55–58.

ORGANIZATIONS

Williams Syndrome Association. PO Box 297, Clawson, MI 48017-0297. (248) 541-3630. Fax: (248) 541-3631. [email protected] <http://www.williams-syndrome.org/>.

Williams Syndrome Foundation. University of California, Irvine, CA 92679-2310. (949)824-7259. <http://www.wsf.org/>.

Kathleen Fergus, MS, CGC

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Williams Syndrome

Williams syndrome

Definition

Williams syndrome is a genetic disorder caused by a deletion of a series of genes on chromosome 7q11. Individuals with Williams syndrome have distinctive facial features, mild mental retardation, heart and blood vessel problems, short stature, unique personality traits, and distinct learning abilities and deficits.

Description

Williams syndrome, also known as Williams Beuren syndrome, was first described in 1961 by Dr. J. C. P. Williams of New Zealand. At that time it was noted that individuals with Williams syndrome had an unusual constellation of physical and mental findings. The physical features include a characteristic facial appearance, heart and cardiovascular problems, high blood calcium levels, low birth weight, short stature, and other connective tissue abnormalities. The intellectual problems associated with Williams include a mild mental retardation and a specific cognitive profile. That is, individuals with Williams syndrome often have the same pattern of learning abilities and disabilities, as well as many similar personality traits.

The findings in Williams syndrome are variable—that is, not all individuals with Williams syndrome will have all of the described findings. In addition to being variable, the physical and mental findings associated with Williams syndrome are progressive—they change over time.

Genetic profile

Williams syndrome is a genetic disorder due to a deletion of chromosome material on the long arm of chromosome 7. A series of genes are located in this region. Individuals with Williams syndrome may have some or all of these genes deleted. Because of this, Williams syndrome is referred to as a contiguous gene deletion syndrome. Contiguous refers to the fact that these genes are arranged next to each other. The size of the deletion can be large or small, which may explain why some individuals with Williams syndrome are more severely affected than others. If you think of these genes as the letters of the alphabet, some individuals with Williams syndrome are missing A to M, some are missing G to Q and others are missing A to R. While there are differences in the amount of genetic material that can be deleted, there is a region of overlap. Everyone in the above example was missing G to M. It is thought that the missing genes in this region are important causes of the physical and mental findings of Williams syndrome.

Two genes in particular, ELN and LIMK1, have been shown to be important in causing some of the characteristic symptoms of Williams syndrome. The ELN gene codes for a protein called elastin. The job of elastin in the human body is to provide elasticity to the connective tissues such as those in the arteries, joints and tendons. The exact role of the LIMK1 gene is not known. The gene codes for a substance known as lim kinase 1 that is active in the brain. It is thought that the deletion of the LIMK1 gene may be responsible for the visuospatial learning difficulties of individuals with Williams syndrome. Many other genes are known to be in the deleted region of chromosome 7q11 responsible for Williams syndrome and much work is being done to determine the role of these genes in Williams syndrome.

Williams syndrome is an autosomal dominant disorder. Genes always come in pairs and in an autosomal dominant disorder, only one gene need be missing or altered for an individual to have the disorder. Although Williams syndrome is an autosomal disorder, most individuals with Williams syndrome are the only people in their family with this disorder. When this is the case, the chromosome deletion that causes Williams syndrome is called de novo. A de novo deletion is one that occurs for the first time in the affected individual. The cause of de novo chromosome deletions is unknown. Parents of an individual with Williams syndrome due to a de novo deletion are very unlikely to have a second child with William syndrome. However, once an individual has a chromosome deletion, there is a 50% chance that they will pass it on to their offspring. Thus individuals with Williams syndrome have a 50% chance of passing this deletion (and Williams syndrome) to their children.

Demographics

Williams syndrome occurs in one in 20,000 births. Because Williams syndrome is an autosomal dominant disorder, it affects an equal number of males and females. It is thought that Williams syndrome occurs in people of all ethnic backgrounds equally.

Signs and symptoms

Williams syndrome is a multi-system disorder. In addition to distinct facial features, individuals with Williams syndrome can have cardiovascular, growth, joint and other physical problems. They also share unique personality traits and have intellectual differences.

Infants with Williams syndrome are often born small for their family and 70% are diagnosed with failure to thrive during infancy. These growth problems continue throughout the life of a person with Williams syndrome and most individuals with Williams syndrome have short stature (height below the third percentile). Infants with William syndrome can also be extremely irritable and have "colic-like" behavior. This behavior is thought to be due to excess calcium in the blood (hypercalcemia). Other problems that can occur in the first years include strabismus (crossed eyes), ear infections, chronic constipation, and eating problems.

Individuals with Williams syndrome can have distinct facial features sometimes described as "elfin" or "pixie-like." While none of these individual facial features are abnormal, the combination of the different features is common for Williams syndrome. Individuals with Williams syndrome have a small upturned nose, a small chin, long upper lip with a wide mouth, small widely spaced teeth and puffiness around the eyes. As an individual gets older, these facial features become more pronounced.

People with Williams syndrome often have problems with narrowing of their heart and blood vessels. This is thought to be due to the deletion of the elastin gene and is called elastin arteriopathy. Any artery in the body can be affected but the most common narrowing is seen in the aorta of the heart. This condition is called supravalvar aortic stenosis (SVAS) and occurs in approximately 75% of individuals with Williams syndrome. The degree of narrowing is variable. If left untreated, it can lead to high blood pressure, heart disease and heart failure. The blood vessels that lead to the kidney and other organs can also be affected.

Deletions of the elastin gene are also thought to be responsible for the loose joints of some children with Williams syndrome. As individuals with Williams syndrome age, their heel cords and hamstrings tend to tighten, which can lead to a stiff awkward gait and curving of the spine.

Approximately 75% of individuals with Williams syndrome have mild mental retardation. They also have a unique cognitive profile (unique learning abilities and disabilities). This cognitive profile is independent of their IQ. Individuals with Williams syndrome generally have excellent language and memorization skills. They can have extensive vocabularies and may develop a thorough knowledge of a topic that they are interested in. Many individuals are also gifted musicians. Individuals with Williams syndrome have trouble with concepts that rely on visuospatial ability. Because of this, many people with Williams syndrome have trouble with math, writing and drawing.

People with Williams syndrome also often share personality characteristics. They are noted to be very talkative and friendly—sometimes inappropriately—and they can be hyperactive. Another shared personality trait is a generalized anxiety.

Diagnosis

The diagnosis of Williams syndrome is usually made by a physician familiar with Williams syndrome and based upon a physical examination of the individual and a review of his or her medical history. It is often made in infants after a heart problem (usually SVAS) is diagnosed. In children without significant heart problems, the diagnosis may be made after enrollment in school when they are noted to be "slow learners."

While a diagnosis can be made based upon physical examination and medical history, the diagnosis can now be confirmed by a DNA test.

Williams syndrome is caused by a deletion of genetic material from the long arm of chromosome 7. A specific technique called fluorescent in situ hybridization testing, or FISH testing, can determine whether there is genetic material missing. A FISH test will be positive (detect a deletion) in over 99% of individuals with Williams syndrome. A negative FISH test for Williams syndrome means that no genetic material is missing from the critical region on chromosome 7q11.

Prenatal testing (testing during pregnancy) for Williams syndrome is possible using the FISH test on DNA sample obtained by chorionic villus sampling (CVS) or by amniocentesis . Chorionic villus sampling is a prenatal test that is usually done between 10 to 12 weeks of pregnancy and involves removing a small amount of tissue from the placenta. Amniocentesis is a prenatal test that is usually performed at 16–18 weeks of pregnancy and involves removing a small amount of the amniotic fluid that surrounds the fetus. DNA is obtained from these samples and tested to see if the deletion responsible for Williams syndrome is present. While prenatal testing is possible, it is not routinely performed. Typically, the test is only done if there is a family history of Williams syndrome.

Treatment and management

Because Williams syndrome is a multi-system disorder, the expertise of a number of specialists is required for management of this disorder.

The height and growth of individuals with Williams syndrome should be monitored using special growth curves developed specifically for individuals with Williams syndrome. Individuals who fall off these growth curves should be worked up for possible eating or thyroid disorders.

A cardiologist should evaluate individuals with Williams syndrome yearly. This examination should include measurement of blood pressure in all four limbs and an echocardiogram of the heart. An echocardiogram is a special form of ultrasound that looks at the structure of the heart. Doppler flow studies, which look at how the blood flows into and out of the heart, should also be done. Individuals with supravalvar stenosis may require surgery to fix this condition. The high blood pressure caused by this condition may be treated with medication. Examinations should take place yearly as some of these conditions are progressive and may worsen over time.

Individuals with Williams syndrome should also have a complete neurological examination. In addition, the blood calcium levels of individuals with Williams syndrome should be monitored every two years. High levels of calcium can cause irritability, vomiting, constipation, and muscle cramps. An individual found to have a high level of calcium should consult a nutritionist to make sure that their intake of calcium is not higher than 100% of the recommended daily allowance (RDA). Because vitamin D can increase calcium levels, individuals with Williams syndrome and high calcium should not take multivitamins containing vitamin D. If calcium levels remain high after limiting vitamin D and decreasing dietary intake of calcium, an individual with hypercalcemia should see a nephrologist for further management and to monitor kidney function.

Strabismus (crossed eyes) can be treated by patching or by surgery. Ear infections can be treated with antibiotics and surgical placement of ear tubes.

The developmental differences of individuals with Williams syndrome should be treated with early intervention and special education classes. Specific learning strategies that capitalize on the strengths of individuals with Williams syndrome should be used. Physical, occupational, and speech therapy should be provided. Behavioral counseling and medication may help with behavioral problems such as hyperactivity and anxiety.

Prognosis

The prognosis for individuals with Williams syndrome is highly dependent on the medical complications of a particular individual. Individuals with Williams syndrome who have no heart complications, or very minor ones, have a good prognosis. Good medical care and treatment of potential problems allows most individuals with Williams syndrome to lead a long life. The prognosis for individuals with more serious medical complications such as severe heart disease or hypertension is more guarded. Since the medical conditions associated with Williams syndrome are progressive rather than static, it is very important that individuals with Williams syndrome have yearly medical examinations with a health care provider familiar with Williams syndrome.

The range of abilities among individuals with Williams syndrome is very wide and the ultimate functioning of an individual is dependent on his or her abilities. While individuals with Williams syndrome do well in structured environments such as school, their unique abilities and disabilities do not permit them to do as well in unstructured surroundings. Some individuals with Williams syndrome live independently but most live with their parents or in a supervised setting. Many individuals with Williams syndrome can gain employment in supervised settings and do well at tasks that do not require mathematics or visuo-spatial abilities. It is important to encourage individuals with Williams syndrome towards independence but to recognize that their friendly and outgoing personalities may lead them into abusive situations.

Resources

BOOKS

Bellugi, Ursula, and Marie St. George. Journey from Cognition to Brain to Gene: Perspectives from Williams Syndrome. Cambridge, MA: MIT Press, 2001.

PERIODICALS

Finn, Robert. "Different Minds." Discover (June 1991): 55-58.

ORGANIZATIONS

Williams Syndrome Association. PO Box 297, Clawson, MI 48017-0297. (248) 541-3630. Fax: (248) 541-3631. [email protected] <http://www.williamssyndrome.org/>.

Williams Syndrome Foundation. University of California, Irvine, CA 92679-2310. (949)824-7259. <http://www.wsf.org/>.

Kathleen Fergus, MS, CGC

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