Angelman Syndrome


What is Angelman syndrome?

Angelman syndrome is a rare genetic disorder that affects the nervous system and causes severe developmental delays, learning disabilities, walking and balance problems, seizures and other health issues. Abnormalities on a specific gene cause Angelman syndrome.

Who is likely to have Angelman syndrome?

Angelman syndrome can affect any racial group or ethnicity. Symptoms usually begin to be noticed when children are between 6 to 12 months of age.

How common is Angelman syndrome?

Angelman syndrome affects one in every 12,000 to 20,000 children born. The syndrome affects both males and females equally.

Symptoms and Causes

What causes Angelman syndrome?

Most cases of Angelman syndrome result from abnormalities of the UBE3A gene. These changes occur early in fetal development, before a baby is born.

A person may have Angelman syndrome symptoms because parts of the UBE3A gene are inactive or missing (about 70 percent of cases). Structural changes to UBE3A may also result in Angelman syndrome (about 11 percent of cases).

Abnormalities of the UBE3A gene usually occur spontaneously, meaning they aren’t inherited. In a small number of cases, children do not inherit a normal copy of chromosome 15 from their mother (for example, they could inherit two copies of chromosome 15 from their father), leading to the development of Angelman syndrome.

In a small percentage of cases, the cause of Angelman syndrome is unknown (about 5 to 10 percent of cases).

What are the symptoms of Angelman syndrome?

Symptoms of Angelman syndrome vary from person to person.

Symptoms that occur in 100 percent of individuals with Angelman syndrome are:

  • Delayed development; learning difficulties
  • Speech problems – ranging from not speaking at all to use of only a few words
  • Movement disorders – arm or leg tremors/jerks; stiff joints; unable to sit upright unsupported
  • Walking difficulties – balance problems, clumsiness, lack of coordination
  • Unique behaviors – A happy manner with frequent smiling and laughing; excitability, often expressed by flapping the hands; restlessness (hyperactive); short attention span

Frequent symptoms that occur in more than 80 percent of individuals with Angelman syndrome include:

  • Seizures (usually starting before 3 years of age)
  • Abnormal electroencephaologram (EEG)
  • Small head circumference (microcephaly)

Other symptoms that occur in 20 to 80 percent of individuals with Angelman syndrome include:

  • Sleeping problems – able to function without much sleep
  • Feeding problems; swallowing difficulty
  • Curvature of the spine (scoliosis), which may worsen as a child ages
  • Unusually pale skin; light-colored eyes and hair
  • Wide mouth with widely spaced teeth
  • Crossed eyes (strabismus)
  • Sticking tongue out
  • Extra chewing/mouthing actions
  • Fascination with water; attraction to shiny or crinkly objects
  • Gastrointestinal tract issues – reflux, constipation
  • Lifting up arms when walking
  • Flat back of head
  • Frequent drooling
  • Increased sensitivity to heat

Diagnosis and Tests

How is Angelman syndrome diagnosed?

Your doctor diagnoses Angelman syndrome with a physical examination and a review of your child’s medical history, signs of developmental delay and presence of other symptoms as noted above. Angelman syndrome is often misdiagnosed as cerebral palsy or autism.

Your doctor may also recommend specific blood tests to check for abnormalities on the UBE3A gene. An EEG may be done if there are concerns about seizures.

Management and Treatment

How is Angelman syndrome treated?

There is no standard treatment for Angelman syndrome. Instead, doctors focus on managing symptoms to maintain the highest possible quality of life. Early diagnosis and treatment is key to helping a child with Angelman syndrome function as normally as possible.

Symptom management may include interventions such as:

  • Anti-seizure medications (anticonvulsants) for those who experience seizures; also a special diet (ketogenic or low glucose index diets)
  • Physical therapy to help with posture, balance, and walking issues and to prevent joint stiffness
  • Use of ankle or foot braces to aid walking; back brace or surgery to manage scoliosis
  • Communication aids and therapies, such as sign language, gesturing, use of special computer communication devices


Can Angelman syndrome be prevented?

There is no way to prevent Angelman syndrome. Angelman syndrome occurs as a result of genetic abnormalities. In most cases, this happens without a known cause. A small percentage of people with Angelman syndrome inherit the disorder.

Outlook / Prognosis

What is the prognosis (outlook) for people with Angelman syndrome?

Most people with Angelman syndrome live nearly as long as people without the condition, however, they are unable to live independently and will need life-long supportive care. Individuals with Angelman syndrome will continue to have intellectual limitations and severe speech impairment throughout their lives. However, some people can learn new communication skills. Some symptoms, such as sleep problems and excitability improve with age.

Effective symptom management helps improve the quality of life for both children and adults affected by Angelman syndrome. Scientists are working toward the possibility of restoring UBE3A function in the brain, though research is still in every early stages.

Living With

What questions should I ask my doctor?

If your child has Angelman syndrome, you may have many questions about the condition. These may include:

  • Which treatments will be best for managing my child’s symptoms?
  • How can I help my child communicate better?
  • Should I have genetic testing or genetic counseling if I plan on having more children?
  • How can I best plan for the support my child will need in the future?
  • Is there a support group nearby for families like ours?


What resources are available for more information about Angelman syndrome?

The following are helpful resources for Angleman syndrome:

Last reviewed by a Cleveland Clinic medical professional on 12/11/2018.


  • Angelman Syndrome Foundation. What is Angelman syndrome? ( Accessed 10/1/2018.
  • National Health Service. Angelman syndrome. ( Accessed 10/1/2018.
  • National Organization for Rare Disorders. Angelman Syndrome. ( Accessed 10/1/2018.
  • U.S. National Library of Medicine. Angelman syndrome. ( Accessed 10/1/2018.

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