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Angelman Syndrome

Angelman syndrome

Definition

Angelman syndrome (AS) is a genetic condition that causes severe mental retardation , severe speech impairment, and a characteristic happy and excitable demeanor.

Description

Individuals with AS show evidence of delayed development by 612 months of age. Eventually, this delay is recognized as severe mental retardation. Unlike some genetic conditions causing severe mental retardation, AS is

not associated with developmental regression (loss of previously attained developmental milestones).

Severe speech impairment is a striking feature of AS. Speech is almost always limited to a few words. However, receptive language skills (listening to and understanding the speech of others) and non-verbal communication are not as severely affected.

Individuals with AS have a balance disorder, causing unstable and jerky movements. This typically includes gait ataxia (a slow, unbalanced way of walking) and tremulous movements of the limbs.

AS is also associated with a unique "happy" behavior, which may be the best-known feature of the condition. This may include frequent laughter or smiling, often with no apparent stimulus. Children with AS often appear happy, excited, and active. They may also sometimes flap their hands repeatedly. Generally, they have a short attention span. These characteristic behaviors led to the original name of this condition, the "Happy Puppet" syndrome. However, this name is no longer used as it is considered insensitive to AS individuals and their families.

Demographics

AS has been reported in individuals of diverse ethnic backgrounds. The incidence of the condition is estimated at 1/10,000 to 1/30,000.

Causes and symptoms

Most cases of AS have been traced to specific genetic defects on chromosomes received from the mother. In about 8% of individuals with AS, no genetic cause can be identified. This may reflect misdiagnosis, or the presence of additional, unrecognized mechanisms leading to AS.

The first abnormalities noted in an infant with AS are often delays in motor milestones (those related to physical skills, such as sitting up or walking), muscular hypotonia (poor muscle tone), and speech impairment. Some infants seem unaccountably happy and may exhibit fits of laughter. By age 12 months, 50% of infants with AS have microcephaly (a small head size). Tremulous movements are often noted during the first year of life.

Seizures occur in 80% of children with AS, usually by three years of age. No major brain lesions are typically seen on cranial imaging studies.

The achievement of walking is delayed, usually occurring between two-and-a-half and six years of age. The child with AS typically exhibits a jerky, stiff gait, often with uplifted and bent arms. About 10% of individuals with AS do not walk. Additionally, children may have drooling, protrusion of the tongue, hyperactivity, and a short attention span.

Many children have a decreased need for sleep and abnormal sleep/wake cycles. This problem may emerge in infancy and persist throughout childhood. Upon awakening at night, children may become very active and destructive to bedroom surroundings.

The language impairment associated with AS is severe. Most children with AS fail to learn appropriate and consistent use of more than a few words. Receptive language skills are less severely affected. Older children and adults are able to communicate by using gestures or communication boards (special devices bearing visual symbols corresponding to commonly used expressions or words).

Some individuals with AS may have a lighter skin complexion than would be expected given their family background.

Diagnosis

The clinical diagnosis of AS is made on the basis of physical examination and medical and developmental history. Confirmation requires specialized laboratory testing.

There is no single laboratory test that can identify all cases of AS. Several different tests may be performed to look for the various genetic causes of AS. When positive, these tests are considered diagnostic for AS. These include DNA methylation studies, UBE3A mutation analysis, and fluorescent in situ hybridization (FISH).

Treatment team

Children with Angelman syndrome will need help from a variety of professionals, including a general pediatrician and pediatric neurologist . A child psychiatrist and/or psychologist may be helpful as well, particularly to help design and implement various behavioral plans. Physical, occupational, and speech and language therapists may help support specific deficits. A learning specialist may be consulted for help with an individualized educational plan.

Treatment

There is no specific treatment for AS. A variety of symptomatic management strategies may be offered for hyperactivity, seizures, mental retardation, speech impairment, and other medical problems.

The typical hyperactivity in AS may not respond to traditional behavior modification strategies. Children with AS may have a decreased need for sleep and a tendency to awaken during the night. Drug therapy may be prescribed to counteract hyperactivity or aid sleep. Most families make special accommodations for their child by providing a safe yet confining environment.

Seizures in AS are usually controllable with one or more anti-seizure medications. In some individuals with severe seizures, dietary manipulations may be tried in combination with medication.

Individuals with AS may be more likely to develop particular medical problems which are treated accordingly. Newborn babies may have difficulty feeding and special bottle nipples or other interventions may be necessary. Gastroesophageal reflux (heartburn) may lead to vomiting or poor weight gain and may be treated with drugs or surgery. Constipation is a frequent problem and is treated with laxative medications. Many individuals with AS have strabismus (crossed eyes), which may require surgical correction. Orthopedic problems, such as tightening of tendons or scoliosis, are common. These problems may be treated with physical therapy, bracing, or surgery.

Prognosis

Individuals with AS have significant mental retardation and speech impairment that are considered to occur in all cases. However, they do have capacity to learn and should receive appropriate educational training.

Young people with AS typically have good physical health aside from seizures. Although life span data are not available, the life span of people with AS is expected to be normal.

Special concerns

Educational concerns

Children with AS appear to benefit from targeted educational training. Physical and occupational therapy may improve the disordered, unbalanced movements typical of AS. Children with a severe balance disorder may require special supportive chairs. Speech therapy is often directed towards the development of nonverbal communication strategies, such as picture cards, communication boards, or basic signing gestures.

Legal issues

The most pressing long-term concern for patients with AS is working out a life plan for ongoing care, since many are likely to outlive their parents. The parents of a child diagnosed with AS should consult an estate planner, an attorney, and a certified public accountant (CPA) in order to draft a life plan and letter of intent. A letter of intent is not a legally binding document, but it gives the patient's siblings and other relatives or caregivers necessary information on providing for her in the future. The attorney can help the parents decide about such matters as guardianship as well as guide them through the legal process of appointing a guardian, which varies from state to state.

Resources

PERIODICALS

"Angelman syndrome." The Exceptional Parent 30, no. 3 (March 2000): S2.

Lombroso, Paul J. "Genetics of Childhood Disorders: XVI. Angelman Syndrome: A Failure to Process." Journal of the American Academy of Child and Adolescent Psychiatry 39, no. 7 (July 2000): 931.

ORGANIZATION

Angelman Syndrome Foundation, Inc. 414 Plaza Drive, Suite 209, Westmont, IL 60559. (800) IF-ANGEL or (630) 734-9267. Fax: (630) 655-0391. [email protected] <http://www.angelman.org>.

WEBSITES

Williams, Charles A., M.D., Amy C. Lossie, Ph.D., and Daniel J. Driscoll, Ph.D. "Angelman Syndrome." (November 21, 2000). GeneClinics. University of Washington, Seattle. <http://www.geneclinics.org/profiles/angelman/details>.

Jennifer Ann Roggenbuck, MS, CGC

Rosalyn Carson-Dewitt, MD

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Angelman's Syndrome

Angelman's syndrome

Definition

Angelman's syndrome is a relatively rare genetic disorder that causes a variety of neurological problems, including developmental delay , seizures, speech impairment, and problems with movement and balance.

Description

Angelman's syndrome was first described in 1965 by Harold Angelman, who noted that a group of children in his medical practice had flat heads, made jerky movements, held their tongues in a protruding way, and had curious bouts of laughter.

Demographics

Angelman's syndrome is relatively rare. As of the early 2000s there were only about 1,000 to 5,000 known cases of the syndrome in the United States. There is no predilection for either sex or for any particular ethnicity.

Causes and symptoms

Most cases of Angelman's syndrome can be traced to a genetic abnormality inherited from a maternal chromosome (15). A particular area of genes that should control the production and function of a protein called ubiquitin is either absent or ineffective. A minority of cases of Angelman's syndrome are due to new mutations in this same area of genes.

Children with Angelman's syndrome have an abnormally small, flat appearance to their skull. By one to two months of age, infants with the syndrome develop feeding difficulties. By six to 12 months, developmental delay is usually noted. Most children develop seizures by three years of age. Other characteristics of the syndrome include abnormally decreased muscle tone, fair skin and hair, protruding jaw, hyperactivity, episodes of uncontrollable laughter, difficulty sleeping, and severe problems with movement and balance. The disorder is sometimes called "happy puppet syndrome," because many children with the disorder have jerky, flapping movements of the arms; a stiff, jerky style of walking (gait); a happy, excited demeanor; and regular episodes of uncontrollable laughter.

Diagnosis

Diagnosis is made by noting the characteristic cluster of symptoms. Careful chromosomal study can reveal abnormalities on chromosome 15 that are consistent with those identified in Angelman's syndrome.

Treatment

As of 2004 there is no cure for Angelman's syndrome. Treatments attempt to ameliorate the symptoms in order to improve the quality of life. Treatments may include anti-seizure medications, physical and occupational therapy, and speech and language therapy.

Prognosis

Most children with Angelman syndrome are severely developmentally delayed. They never acquire normal speech, and they require care and supervision throughout their lives.

KEY TERMS

Ataxia A condition marked by impaired muscular coordination, most frequently resulting from disorders in the brain or spinal cord.

Developmental delay The failure of a child to meet certain developmental milestones, such as sitting, walking, and talking, at the average age. Developmental delay may indicate a problem in development of the central nervous system.

Prevention

There are no methods to prevent Angelman syndrome. However, if the disorder is known to run in a family , genetic counseling may help parents evaluate their level of risk for having a child with this disorder. Specialized testing of chromosome 15 will be required; the usual tests done during amniocentesis or chorionic villi sampling will not reveal the specific, small genetic flaw that causes Angelman syndrome.

Parental concerns

Caring for a child with Angelman syndrome constitutes a complex challenge. Parents should be encouraged to seek out parental and sibling support groups and respite care in order to help them face these challenges.

Resources

BOOKS

Hall, Judith G. "Chromosomal Clinical Abnormalities." In Nelson Textbook of Pediatrics. Edited by Richard E. Behrman, et al. Philadelphia: Saunders, 2004.

Jankovic, Joseph. "Movement Disorders." In Textbook of Clinical Neurology. Edited by Christopher G. Goetz. Philadelphia: Saunders, 2003.

PERIODICALS

Didden, R. "Sleep problems in individuals with Angelman syndrome." In American Journal of Mental Retardation 109 (July 2004): 27584.

Oliver, C. "Effects of environmental events on smiling and laughing behavior in Angelman syndrome." In American Journal of Mental Retardation 107 (May 2002): 194200.

Peters, S. U. "Cognitive and adaptive behavior profiles of children with Angelman syndrome." In American Journal of Medical Genetics 128A (July 2004): 1103.

ORGANIZATIONS

American Academy of Pediatrics. 141 Northwest Point Blvd., Elk Grove Village, IL 60007-1098. Web site: <www.aap.org>.

WEB SITES

"Angelman Syndrome: Just because I can't talk doesn't mean I don't have anything to say." Available online at <www.armyofangels.org/> (accessed December 19, 2004).

"Facts about Angelman Syndrome: Information for Families [Internet links]." Available online at <www.asclepius.com/angel/asinfo.html> (accessed December 19, 2004).

Rosalyn Carson-DeWitt, MD

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Angelman syndrome

Angelman syndrome (happy puppet syndrome) (ayn-jĕl-măn) n. a disorder characterized by severe developmental delay, absence of speech, seizures, a jerky puppet-like gait, and paroxysmal laughter. It is usually caused by an abnormality of maternal chromosome 15.[ H. Angelman (1915–96), British paediatrician]

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Angelman syndrome

Angelman syndrome

Definition

Angelman syndrome (AS) is a genetic condition that causes severe mental retardation, severe speech impairment, and a characteristic happy and excitable demeanor.

Description

Individuals with AS show evidence of delayed development by 6–12 months of age. Eventually, this delay is recognized as severe mental retardation. Unlike some genetic conditions causing severe mental retardation, AS is not associated with developmental regression (loss of previously attained developmental milestones).

Severe speech impairment is a striking feature of AS. Speech is almost always limited to a few words or no words at all. However, receptive language skills (listening to and understanding the speech of others) and non-verbal communication are not as severely affected.

Individuals with AS have a balance disorder, causing unstable and jerky movements. This typically includes gait ataxia (a slow, unbalanced way of walking) and tremulous movements of the limbs.

AS is also associated with a unique "happy" behavior, which may be the best-known feature of the condition. This may include frequent laughter or smiling, often with no apparent stimulus. Children with AS often appear happy, excited, and active. They may also sometimes flap their hands repeatedly. Generally, they have a short attention span. These characteristic behaviors led to the original name of this condition, the "Happy Puppet" syndrome. However, this name is no longer used as it is considered insensitive to AS individuals and their families.

Genetic profile

The genetics of AS are complex. There are at least five different genetic abnormalities that can cause the condition, all of which involve a specific region of the chromosome 15 inherited from the mother. This region is designated 15q11-13 (bands 11 through 13 on the long arm of chromosome 15). The fact that AS occurs only when there are abnormalities in this region of the maternal copy of chromosome 15 reflects a unique phenomenon known as imprinting. Imprinting is a chemical modification of DNA which acts as an "identification tag" indicating which parent contributed the chromosome. Imprinted genes or chromosome regions are expressed or not expressed depending on which parent transmitted the chromosome. Abnormalities in the paternally inherited 15q11-13 region (from the father) cause a different genetic condition called Prader-Willi syndrome .

Chromosome deletion

The most common cause of AS is a small deletion (missing piece) in the maternally inherited chromosome 15. Specifically, the deletion occurs within 15q11-13. Approximately 70% of AS individuals have this deletion.

UBE3A mutation

In approximately 11% of AS cases, there is a mutation within the maternally inherited UBE3A gene . All the genetic mechanisms leading to AS appear to compromise expression of this gene, which is located within the 15q11-13 region. This gene is considered to be the "critical gene" responsible for AS, although its specific function is unknown.

Uniparental disomy

Some cases of AS result from inheritance of both chromosomes in the 15 pair from the father, an unusual genetic phenomenon known as uniparental disomy. In this circumstance, there is no chromosome 15 from the mother. Approximately 7% of AS cases result from this mechanism.

Imprinting defect

Approximately 3% of AS cases result from an imprinting defect on the maternally inherited chromosome 15. As noted above, imprinting is a chemical modification to the DNA which serves as a marker indicating the parent of origin and controls gene expression. If there is defective imprinting on the maternally inherited 15, then the genes in the 15q11-15q13 region may not be expressed, leading to AS.

Chromosome rearrangement

Rarely, AS may be caused by chromosomal breaks that occur in the maternal inherited 15q11-13 region. The breaks may occur as the result of a translocation (in which two chromosomes break and exchange material) or an inversion (in which a piece of a chromosome breaks and rejoins in the opposite orientation), or other disturbance of the chromosome structure involving the maternal 15q11-15q13. This mechanism is responsible for about 1% of AS cases.

Unknown mechanism(s)

In about 8% of individuals with AS, no genetic cause can be identified. This may reflect misdiagnosis, or the presence of additional, unrecognized mechanisms leading to AS.

Demographics

AS has been reported in individuals of diverse ethnic backgrounds. The incidence of the condition is estimated at 1/10,000 to 1/30,000.

Signs and symptoms

The first abnormalities noted in an infant with AS are often delays in motor milestones (those related to physical skills, such as sitting up or walking), muscular hypotonia (poor muscle tone), and speech impairment. Some infants seem unaccountably happy and may exhibit fits of laughter. By age 12 months, 50% of infants with AS have microcephaly (a small head size). Tremulous movements are often noted during the first year of life.

Seizures occur in 80% of children with AS, usually by three years of age. No major brain lesions are typically seen on cranial imaging studies.

The achievement of walking is delayed, usually occurring between two-and-a-half and six years of age. The child with AS typically exhibits a jerky, stiff gait, often with uplifted and bent arms. About 10% of individuals with AS do not walk. Additionally, children may have drooling, protrusion of the tongue, hyperactivity, and a short attention span.

Many children have a decreased need for sleep and abnormal sleep/wake cycles. This problem may emerge in infancy and persist throughout childhood. Upon awakening at night, children may become very active and destructive to bedroom surroundings.

The language impairment associated with AS is severe. Most children with AS fail to learn appropriate and consistent use of more than a few words. Receptive language skills are less severely affected. Older children and adults are able to communicate by using gestures or communication boards (special devices bearing visual symbols corresponding to commonly used expressions or words).

Some individuals with AS caused by a deletion of the 15q11-q13 chromosomal region may have a lighter skin complexion than would be expected given their family background.

Diagnosis

The clinical diagnosis of AS is made on the basis of physical examination and medical and developmental history. Confirmation requires specialized laboratory testing.

There is no single laboratory test that can identify all cases of AS. Several different tests may be performed to look for the various genetic causes of AS. When positive, these tests are considered diagnostic for AS.

DNA methylation studies

DNA methylation studies determine if the normal imprinting pattern associated with the maternal (mother's) copy of the number 15 chromosome is present. The 15q11-q13 region is differently methylated (or "imprinted") depending on which parent contributed the chromosome. If an individual has a deletion of this region on the maternal chromosome 15, paternal uniparental disomy of the number 15 chromosomes (with no number 15 chromosome from the mother), or a defective imprinting mechanism, DNA methylation studies will be abnormal and indicate AS. This test detects the majority (approximately 78%) of cases of AS. Additional studies are then required to determine which of these three mechanisms lead to AS development.

UBE3A mutation analysis

Direct DNA testing of the UBE3A gene is necessary to detect cases of AS caused by mutations in this gene. Cases of AS caused by UBE3A mutations usually have a normal imprinting pattern.

Fluorescent in situ hybridization (FISH)

FISH studies may be necessary to detect chromosome rearrangements that disrupt the 15q11-q13 region on the maternal copy of chromosome 15. The FISH method is a special way of checking for the presence, absence, or rearrangement of very small pieces of chromosomes. FISH testing can also readily detect AS caused by chromosome deletions, which account for approximately 70% of AS cases. FISH testing is often performed following an abnormal methylation study to determine if a chromosome deletion accounts for the abnormal methylation pattern.

Treatment and management

There is no specific treatment for AS. A variety of symptomatic management strategies may be offered for hyperactivity, seizures, mental retardation, speech impairment, and other medical problems.

The typical hyperactivity in AS may not respond to traditional behavior modification strategies. Children with AS may have a decreased need for sleep and a tendency to awaken during the night. Drug therapy may be prescribed to counteract hyperactivity or aid sleep. Most families make special accommodations for their child by providing a safe yet confining environment.

Seizures in AS are usually controllable with one or more anti-seizure medications. In some individuals with severe seizures, dietary manipulations may be tried in combination with medication.

Children with AS appear to benefit from targeted educational training. Physical and occupational therapy may improve the disordered, unbalanced movements typical of AS. Children with a severe balance disorder may require special supportive chairs. Speech therapy is often directed towards the development of nonverbal communication strategies, such as picture cards, communication boards, or basic signing gestures.

Individuals with AS may be more likely to develop particular medical problems which are treated accordingly. Newborn babies may have difficulty feeding and special bottle nipples or other interventions may be necessary. Gastroesophageal reflux (heartburn) may lead to vomiting or poor weight gain and may be treated with drugs or surgery. Constipation is a frequent problem and is treated with laxative medications. Many individuals with AS have strabismus (crossed eyes), which may require surgical correction. Orthopedic problems, such as tightening of tendons or scoliosis , are common. These problems may be treated with physical therapy, bracing, or surgery.

Prognosis

Individuals with AS have significant mental retardation and speech impairment that are considered to occur in all cases. However, they do have capacity to learn and should receive appropriate educational training.

Young people with AS typically have good physical health aside from seizures. Although life span data are not available, the life span of people with AS is expected to be normal.

Resources

PERIODICALS

"Angelman syndrome." The Exceptional Parent 30, no. 3 (March 2000): S2.

Lombroso, Paul J. "Genetics of Childhood Disorders: XVI. Angelman Syndrome: A Failure to Process." Journal of the American Academy of Child and Adolescent Psychiatry 39, no. 7 (July 2000): 931.

ORGANIZATION

Angelman Syndrome Foundation, Inc. 414 Plaza Drive, Suite 209, Westmont, IL 60559. (800) IF-ANGEL or (630) 734-9267. Fax: (630) 655-0391. [email protected] <http://www.angelman.org>.

WEBSITES

Williams, Charles A., M.D., Amy C. Lossie, Ph.D., and Daniel J. Driscoll, Ph.D. "Angelman Syndrome.". (November 21, 2000). GeneClinics. University of Washington, Seattle. <http://www.geneclinics.org/profiles/angelman/details>.

Jennifer Ann Roggenbuck, MS, CGC

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Notes:
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Angelman Syndrome

Angelman syndrome

Definition

Angelman syndrome (AS) is a genetic condition that causes severe mental retardation, severe speech impairment, and a characteristic happy and excitable demeanor.

Description

Individuals with AS show evidence of delayed development by 6–12 months of age. Eventually, this delay is recognized as severe mental retardation. Unlike some genetic conditions causing severe mental retardation, AS is not associated with developmental regression (loss of previously attained developmental milestones).

Severe speech impairment is a striking feature of AS. Speech is almost always limited to a few words or no words at all. However, receptive language skills (listening to and understanding the speech of others) and non-verbal communication are not as severely affected.

Individuals with AS have a balance disorder, causing unstable and jerky movements. This typically includes gait ataxia (a slow, unbalanced way of walking) and tremulous movements of the limbs.

AS is also associated with a unique "happy" behavior, which may be the best-known feature of the condition. This may include frequent laughter or smiling, often with no apparent stimulus. Children with AS often appear happy, excited, and active. They may also sometimes flap their hands repeatedly. Generally, they have a short attention span. These characteristic behaviors led to the original name of this condition, the "Happy Puppet" syndrome. However, this name is no longer used as it is considered insensitive to AS individuals and their families.

Genetic profile

The genetics of AS are complex. There are at least five different genetic abnormalities that can cause the condition, all of which involve a specific region of the chromosome 15 inherited from the mother. This region is designated 15q11-13 (bands 11 through 13 on the long arm of chromosome 15). The fact that AS occurs only when there are abnormalities in this region of the maternal copy of chromosome 15 reflects a unique phenomenon known as imprinting . Imprinting is a chemical modification of DNA which acts as an "identification tag" indicating which parent contributed the chromosome. Imprinted genes or chromosome regions are expressed or not expressed depending on which parent transmitted the chromosome. Abnormalities in the paternally (from the father) inherited 15q11-13 region cause a different genetic condition called Prader-Willi syndrome .

Chromosome deletion

The most common cause of AS is a small deletion (missing piece) in the maternally inherited chromosome 15. Specifically, the deletion occurs within 15q11-13. Approximately 70% of AS individuals have this deletion.

UBE3A mutation

In approximately 11% of AS cases, there is a mutation within the maternally inherited UBE3A gene . All the genetic mechanisms leading to AS appear to compromise expression of this gene, which is located within the 15q11-13 region. This gene is considered to be the "critical gene" responsible for AS, although its specific function is unknown.

Uniparental disomy

Some cases of AS result from inheritance of both chromosomes in the 15 pair from the father, an unusual genetic phenomenon known as uniparental disomy. In this circumstance, there is no chromosome 15 from the mother. Approximately 7% of AS cases result from this mechanism.

Imprinting defect

Approximately 3% of AS cases result from an imprinting defect on the maternally inherited chromosome 15. As noted above, imprinting is a chemical modification to the DNA which serves as a marker indicating the parent of origin and controls gene expression. If there is defective imprinting on the maternally inherited 15, then the genes in the 15q11-15q13 region may not be expressed, leading to AS.

Chromosome rearrangement

Rarely, AS may be caused by chromosomal breaks that occur in the maternal inherited 15q11-13 region. The breaks may occur as the result of a translocation (in which two chromosomes break and exchange material) or an inversion (in which a piece of a chromosome breaks and rejoins in the opposite orientation), or other disturbance of the chromosome structure involving the maternal 15q11-15q13. This mechanism is responsible for about 1% of AS cases.

Unknown mechanism(s)

In about 8% of individuals with AS, no genetic cause can be identified. This may reflect misdiagnosis, or the presence of additional, unrecognized mechanisms leading to AS.

Demographics

AS has been reported in individuals of diverse ethnic backgrounds. The incidence of the condition is estimated at 1/10,000 to 1/30,000.

Signs and symptoms

The first abnormalities noted in an infant with AS are often delays in motor milestones (those related to physical skills, such as sitting up or walking), muscular hypotonia (poor muscle tone), and speech impairment. Some infants seem unaccountably happy and may exhibit fits of laughter. By age 12 months, 50% of infants with AS have microcephaly (a small head size). Tremulous movements are often noted during the first year of life.

Seizures occur in 80% of children with AS, usually by three years of age. No major brain lesions are typically seen on cranial imaging studies.

The achievement of walking is delayed, usually occurring between two-and-a-half and six years of age. The child with AS typically exhibits a jerky, stiff gait, often with uplifted and bent arms. About 10% of individuals with AS do not walk. Additionally, children may have drooling, protrusion of the tongue, hyperactivity, and a short attention span.

Many children have a decreased need for sleep and abnormal sleep/wake cycles. This problem may emerge in infancy and persist throughout childhood. Upon awakening at night, children may become very active and destructive to bedroom surroundings.

The language impairment associated with AS is severe. Most children with AS fail to learn appropriate and consistent use of more than a few words. Receptive language skills are less severely affected. Older children and adults are able to communicate by using gestures or communication boards (special devices bearing visual symbols corresponding to commonly used expressions or words).

Some individuals with AS caused by a deletion of the 15q11-q13 chromosomal region may have a lighter skin complexion than would be expected given their family background.

Diagnosis

The clinical diagnosis of AS is made on the basis of physical examination and medical and developmental history. Confirmation requires specialized laboratory testing.

There is no single laboratory test that can identify all cases of AS. Several different tests may be performed to look for the various genetic causes of AS. When positive, these tests are considered diagnostic for AS.

DNA methylation studies

DNA methylation studies determine if the normal imprinting pattern associated with the maternal (mother's) copy of the number 15 chromosome is present. The 15q11-q13 region is differently methylated (or "imprinted") depending on which parent contributed the chromosome. If an individual has a deletion of this region on the maternal chromosome 15, paternal uniparental disomy of the number 15 chromosomes (with no number 15 chromosome from the mother), or a defective imprinting mechanism, DNA methylation studies will be abnormal and indicate AS. This test detects the majority (approximately 78%) of cases of AS. Additional studies are then required to determine which of these three mechanisms lead to AS development.

UBE3A mutation analysis

Direct DNA testing of the UBE3A gene is necessary to detect cases of AS caused by mutations in this gene. Cases of AS caused by UBE3A mutations usually have a normal imprinting pattern.

Fluorescent in situ hybridization (FISH)

FISH studies may be necessary to detect chromosome rearrangements that disrupt the 15q11-q13 region on the maternal copy of chromosome 15. The FISH method is a special way of checking for the presence, absence, or rearrangement of very small

pieces of chromosomes. FISH testing can also readily detect AS caused by chromosome deletions, which account for approximately 70% of AS cases. FISH testing is often performed following an abnormal methylation study to determine if a chromosome deletion accounts for the abnormal methylation pattern.

Treatment and management

There is no specific treatment for AS. A variety of symptomatic management strategies may be offered for hyperactivity, seizures, mental retardation, speech impairment, and other medical problems.

The typical hyperactivity in AS may not respond to traditional behavior modification strategies. Children with AS may have a decreased need for sleep and a tendency to awaken during the night. Drug therapy may be prescribed to counteract hyperactivity or aid sleep. Most families make special accommodations for their child by providing a safe yet confining environment.

Seizures in AS are usually controllable with one or more anti-seizure medications. In some individuals with severe seizures, dietary manipulations may be tried in combination with medication.

Children with AS appear to benefit from targeted educational training. Physical and occupational therapy may improve the disordered, unbalanced movements typical of AS. Children with a severe balance disorder may require special supportive chairs. Speech therapy is often directed towards the development of nonverbal communication strategies, such as picture cards, communication boards, or basic signing gestures.

Individuals with AS may be more likely to develop particular medical problems which are treated accordingly. Newborn babies may have difficulty feeding and special bottle nipples or other interventions may be necessary. Gastroesophageal reflux (heartburn) may lead to vomiting or poor weight gain and may be treated with drugs or surgery. Constipation is a frequent problem and is treated with laxative medications. Many individuals with AS have strabismus (crossed eyes), which may require surgical correction. Orthopedic problems, such as tightening of tendons or scoliosis , are common. These problems may be treated with physical therapy, bracing, or surgery.

Prognosis

Individuals with AS have significant mental retardation and speech impairment that are considered to occur in all cases. However, they do have capacity to learn and should receive appropriate educational training.

Young people with AS typically have good physical health aside from seizures. Although life span data are not available, the life span of people with AS is expected to be normal.

Resources

PERIODICALS

"Angelman syndrome." The Exceptional Parent 30, no. 3 (March 2000): S2.

Lombroso, Paul J. "Genetics of Childhood Disorders: XVI. Angelman Syndrome: A Failure to Process." Journal of the American Academy of Child and Adolescent Psychiatry 39, no. 7 (July 2000): 931.

ORGANIZATION

Angelman Syndrome Foundation, Inc. 414 Plaza Drive, Suite 209, Westmont, IL 60559. (800) IF-ANGEL or (630) 734-9267. Fax: (630) 655-0391. [email protected] <http://www.angelman.org>.

WEBSITES

Williams, Charles A., M.D., Amy C. Lossie, Ph.D., and Daniel J. Driscoll, Ph.D. "Angelman Syndrome." (November 21, 2000). GeneClinics. University of Washington, Seattle. <http://www.geneclinics.org/profiles/angelman/details>.

Jennifer Ann Roggenbuck, MS, CGC

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