Medical Management Considerations
Resources for Families
Advisory Committee
Publication Information

Learning Points

  • Restate the occurrence of Angelman Syndrome (1 in 20,000 births).
  • Recognize eight characteristic features of Angelman Syndrome; e.g.,
    • Severe developmental delay evident by 6-12 months of age (100%)
    • Severe mental retardation (100%)
    • Profound speech impairment (98%)
    • Stiff, jerky gait with legs wide and arms up
    • Microcephaly by age 2 (90%)
    • Seizures by age 3 (80%)
    • Truncal hypotonia (90%)
    • Limb hypertonia (85%)
  • Select appropriate diagnostic studies to detect Angelman Syndrome [e.g., high resolution chromosome analysis to rule out other chromosomal disorders; fluorescent in situ hybridization (FISH) analysis to detect deletion on chromosome 15].
  • Describe several ongoing recommended care plan components appropriate for all ages (e.g., using nonverbal communication methods; monitoring for seizures; monitoring for scoliosis; considering surgery for flexion contractures; monitoring for gastroesophageal reflux disease, etc.).
  • Refer families to appropriate resources on Angelman Syndrome.


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Description and Cause

Angelman Syndrome is a genetic disorder characterized by physical abnormalities and impairments in neurological, motor, and intellectual functioning. It may be caused by (1) maternal deletion on the long arm of chromosome 15 in up to 80% of cases; (2) uniparental disomy (both chromosomes 15 of paternal origin) in 3-4% of cases; (3) an imprinting defect or genetic mutation in 5% of cases; or (4) an unknown cause in 10-15% of cases. (Note: Prader-Willi Syndrome is often discussed with Angelman Syndrome because they share a similar genetic basis; return to the index to view a document on Prader-Willi Syndrome.)


  • 1:20,000 births (It is believed that Angelman Syndrome is widely underdiagnosed.)
  • Recurrence risk: <1%


  1. High resolution chromosome analysis to rule out other chromosomal disorders
  2. Fluorescent in situ hybridization (FISH) analysis to detect deletion on chromosome 15
  3. Additional molecular and/or genetic testing to detect other causes

Characteristic Features

  • Severe developmental delay evident by 6-12 months of age (100%)
  • Severe mental retardation (100%)
  • Profound speech impairment (98%) (absent speech in 88%; others may speak up to 20 words but usually without meaning)
  • Stiff, jerky gait with legs wide and arms up
  • Microcephaly by age 2 (90%)
  • Seizures by age 3 (80%)
  • Truncal hypotonia (90%)
  • Limb hypertonia (85%)
  • Hypermotor behavior
  • Feeding problems in infancy (75%)
  • Hypopigmented skin and eyes (65-90%)
  • Prominent mandible (95%)
  • Flattened back of head (90%
  • Wide mouth (75%)
  • Protruding tongue (70%)
  • Small, widely-spaced teeth (60%)
  • Strabismus (40%)
  • Sleep disturbances
  • Excessive drooling, chewing/mouthing
  • Happy demeanor, excessive laughter/smiling
  • Fascination with water and plastic
  • Hand flapping
  • Increased sensitivity to heat
  • Behavioral problems (attention deficit, hyperactivity, aggression, noncompliance)

Common Associations

  • Autism
  • Epilepsy
  • Scoliosis by age 5 (10%)
  • Suck/swallowing disorders
  • Gastrointestinal disorders
  • Attention Deficit and Hyperactivity Disorder


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Note: These considerations are in addition to the normal medical care provided to an individual without Angelman Syndrome. All recommendations can be addressed through clinical examination by the primary care provider, unless otherwise noted.

Because persons with Angelman Syndrome often exhibit profound communication deficits, inattentiveness and hyperactivity, many clinicians, educators and caregivers assume that profound functional impairment is inevitable. However, affected individuals may overcome many challenges and achieve developmental progress if appropriate interventions are delivered. It is important to emphasize nonverbal skills in measuring cognitive capabilities; although speech is absent or extremely limited, most individuals are able to understand verbal language very well. Many individuals with Angelman Syndrome are able to participate in group activities, perform household chores, and provide self-care. Typically, the primary care physician’s main focus is on seizure management.

Upon Diagnosis

Note: Diagnosis is usually not made until after 12 months of age, and may not be made until late childhood or adulthood. In any case, the following should be performed as soon as diagnosis is suspected.

  • Perform complete physical and neurological exam to detect congenital anomalies
  • Refer for physical and occupational therapy evaluation
  • Refer for speech and language therapy evaluation if over 12 months of age
  • Provide genetic counseling, including discussion of recurrence risk
  • Refer to early intervention programs and Angelman Syndrome/disability support groups
  • Discuss possibility of SSI enrollment

Ongoing (all ages)

  • Recommend use of nonverbal communication methods: sign language, body language, picture cards, sounds, augmentative devices, etc. (although many individuals may not have sufficient attention span or communication skills to use these techniques)
  • Monitor for seizures; prescribe standard anticonvulsant medications if seizures occur (return to index to view a document on Epilepsy)
  • Monitor for scoliosis
  • Consider surgery for flexion contractures
  • Consider behavioral or psychopharmaco-logic options for managing challenging behaviors including overactivity
  • Monitor sleep patterns
  • Monitor for gastroesophageal reflux disease (return to index to view a document on reflux)
  • Consider bracing or surgery to properly align legs if necessary
  • Encourage self-care skills

Childhood (1 to 13 years)

  • Recommend speech and language therapy
  • Recommend and arrange for dental care
  • Recommend behavior modification therapy evaluation if needed
  • Monitor school progress
  • Recommend structured environments and schedules at school and home, with an emphasis on individualized learning
  • Encourage daily walking and exercising to prevent loss of ability to walk
  • Monitor speech and language progress
  • Refer for psychiatric evaluation if needed

Adolescence and Adulthood (13 years and over)

  • Reinforce importance of self-care skills
  • Discuss long-term financial plans
  • Discuss alternative community living resources
  • Monitor prevocational training and vocational activities
  • Discuss community-supported employment opportunities


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Peer-reviewed Journal Articles/Academies

Buckley, R.H. et al. (1998). Angelman Syndrome: Are the Estimates Too Low? American Journal of Medical Genetics, 80(4), 385-390.

Cassidy, S.B., Schwartz, S. (1998). Prader-Willi and Angelman Syndromes: Disorders of Genomic Imprinting. Medicine, 77(2), 140-151.

Malcolm, S, et al. (1991). Uniparental Paternal Disomy in Angelman’s Syndrome. Lancet, 337(8743), 694-697.

Penner, K.A. et al. (1993). Communication, Cognition, and Social Integration in the Angelman Syndrome. American Journal of Medical Genetics, 46, 34-39.

Summers, J.A. et al. (1995). Behaviour Problems in Angelman Syndrome. Journal of Intellectual Disability Research, 39(2), 97-106.

Special Interest Groups/Other Publications

Angelman Syndrome Foundation (USA). Facts About Angelman Syndrome. Accessed March 29, 1999

Capute, A.J., Accardo, P.J. (1996). Developmental Disabilities in Infancy and Childhood vol. I: Neurodevelopmental Diagnosis and Treatment. Baltimore: Paul H. Brookes.

Capute, Arnold J. and Pasquale J. Accardo. (1996). Developmental Disabilities in Infancy and Childhood vol II: The Spectrum of Developmental Disabilities. Baltimore: Paul H. Brookes.

Miller, L. (1995). (revised 1999). Angelman Syndrome: A Parent’s Guide. (Master’s thesis). Accessed March 29, 1999 at [Note: site no longer exists] Spanish version available


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Angelman Syndrome Foundation

California Department of Developmental Services

California Regional Centers

Canadian Angelman Syndrome Society

Exceptional Parent Magazine

March of Dimes Birth Defects Foundation


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Theodore A. Kastner, M.D., M.S.
Felice Weber Parisi, M.D., M.P.H.
Romie H. Holland, M.D.
Patricia Samuelson, M.D.


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This document does not provide advice regarding medical diagnosis or treatment for any individual case, and any opinions or statements contained in this document are not intended to serve as a standard of medical care. Physicians are encouraged to view the considerations presented in this document in light of evolving scientific information. This document is not intended for use by the layperson. Reproduction of this document may be done with proper credit given to California Department of Developmental Services.