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Angelman Syndrome
Monday, 23 June 2003
Tuesday, 17 May 2005


Angelman syndrome is a genetic disorder that is characterized by severe learning difficulties, seizures, uncoordinated movements, and a very happy demeanor.


Angelman syndrome occurs in all ethnic groups and equally affects both males and females. The disease occurs in about 1 in 12,000 to 1 in 20,000 births.

Signs and Symptoms

Angelman syndrome is present at birth but is commonly not recognized right away because the pregnancy and birth are usually normal. The first signs of Angelman syndrome are usually in the first year of life when the child displays developmental delays, low muscle tone, and a slowing of head growth. The most common age of diagnosis is 3-7 years old. More than 80% of children have onset of seizures before the age of three. The type of seizures varies. Children can experience full body seizures with jerking of the arms and legs, or they can have seizures that just show periods of lack of awareness, or anything in between. The child does not achieve developmental milestones as expected. Language typically does not develop in children with Angelman syndrome. Most can understand simple commands, but are only able to communicate through gestures. Very few children are able to speak more than two or three words. There are physical characteristics that are common in children with Angelman syndrome. For example, they may have crossed eyes, a wide mouth, widely spaced teeth, a protruding tongue, large jaw, and lighter colored skin, eyes, and hair as compared to other family members. When they walk, they have problems with balance, are stiff, and hold their arms and hands flexed. Angelman syndrome can cause a variety of behavioral characteristics. Some of these include frequent laughter and smiling, hyperactivity, short attention span, difficulty sleeping, and hand-flapping movements. There may also be a strong attraction to and fascination with water, reflective surfaces, plastic objects, and balloons. Children typically enjoy being around other people and watching TV, especially slap-stick comedy.

Possible Causes

The most common cause of Angelman syndrome is found in about 70% of children. This results from a deletion (missing piece) of a part of chromosome 15. We each have two copies of chromosome 15, one from our mother and one from our father. Angelman syndrome occurs if the deletion is on the chromosome that is inherited from the mother. The second most common cause of Angelman syndrome is found in about 11% of children. This results from a mutation (change) in a gene called UBE3A. The UBE3A gene is also located in the same region of chromosome 15 that is described above. A third cause of Angelman syndrome is found in about 7% of children. This results from inheriting both copies of chromosome 15 from the father. This is called “uniparental disomy” (UPD). A fourth cause of Angelman syndrome is found in about 0.5% of children. This results if chromosome 15 does not function properly. This is referred to as an “imprinting” defect. Less than 1% of children with Angelman syndrome have another chromosome rearrangement (abnormality). In about 10% of cases, the cause of Angelman syndrome is unknown. There are research reports that have found an increased risk of Angelman syndrome associated with artificial reproductive technology.


: When diagnosing Angelman Syndrome, chromosome analysis is done to verify that there are no other chromosome abnormalities besides chromosome 15. Several tests can be performed to confirm the diagnosis. DNA methylation testing can test for the most common causes of Angelman Syndrome, including deletions, uniparental disomy, or imprinting defects. This test will diagnose about 80% of individuals. A fluorescent in situ hybridization (FISH) test can be performed to look for a deletion on chromosome 15. Testing of the UBE3A gene will diagnose about 11% of individuals.


There is no cure for Angelman syndrome. It is important for the child to receive therapy for the physical and behavioral problems associated with the disease. The child’s environment should be safe so that the child isn’t injured during the hyperactive behaviors. Seizures can often be difficult to treat with anti-seizure medications. Medications may be tried to help with sleep and/or constipation. Programs for the special educational needs of the children are usually helpful. If the individual develops scoliosis or other bone or joint problems, he or she should be treated by an orthopedist. Strabismus (or cross-eyes) may require surgery. Older children have a tendency for obesity and so diet should be monitored.


The facial characteristics of Angelman syndrome become more pronounced in adulthood. The ability to move around often decreases as the individual gets older and they may need a wheelchair. The life span of individuals with Angelman syndrome is usually normal but they are unable to live independently. They have relatively good health except for the seizures. They may have problems with constipation, scoliosis (curves in the back or spine), and/or obesity.

Connect with other parents

In the spirit of community and support, Madisons Foundation offers the unique service of connecting parents of children with rare diseases. If you would like to be connected to other parents of children with this disease, please fill out this brief form.


Angelman Syndrome Foundation
This is an informative website for families. It provides information about the disease as well as support for families.

Australian Angelman Syndrome Association
This website is organized in a simple manner. It has less information about the disease than other sites, but it may be easier for parents to navigate. It is good for answering common questions.

Angelman Syndrome Information for Families and Professionals
A well organized website with medical information, an easily understood genetics section and many links to other website and support groups.

Google Search for Angelman Syndrome

References and Sources

Clayton-Smith, J and Laan, L.. Angelman syndrome: a review of the clinical and genetic aspects. Journal of Medical Genetics, Feb 2003 40(2):87-95. McKusick, V. #105830 Angelman Syndrome. Online Mendelian Inheritance in Man. GeneReviews: Angelman Syndrome.