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Genetic and Rare Diseases Information Center (GARD)

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Angelman syndrome


Other Names for this Disease

  • AS
  • Happy puppet syndrome (formerly)
See Disclaimer regarding information on this site. Some links on this page may take you to organizations outside of the National Institutes of Health.

Overview

What is Angelman syndrome?

What causes Angelman syndrome?

How might Angelman syndrome be inherited?

What is Angelman syndrome?

Angelman syndrome is a genetic disorder that primarily affects the nervous system. Characteristic features of this condition include developmental delay, intellectual disability, severe speech impairment, problems with movement and balance (ataxia), epilepsy, and a small head size. Individuals with Angelman syndrome typically have a happy, excitable demeanor with frequent smiling, laughter, and hand-flapping movements. Many of the characteristic features of Angelman syndrome result from the loss of function of a gene called UBE3A. Most cases of Angelman syndrome are not inherited, although in rare cases a genetic change responsible for Angelman syndrome can be inherited from a parent.[1]
Last updated: 6/13/2011

What causes Angelman syndrome?

Angelman syndrome is caused by a loss of function of a gene called UBE3A on chromosome 15. The exact mechanism that causes this loss of function is complex. People normally inherit one copy of the UBE3A gene from each parent. Both copies of this gene are turned on (active) in many of the body's tissues. In certain areas of the brain, however, only the copy inherited from a person's mother is active. This parent-specific gene activation is known as genomic imprinting. If the maternal copy of the UBE3A gene is lost because of a chromosomal change or a gene mutation, a person will have no active copies of the gene in some parts of the brain.[1]

Several different genetic mechanisms can inactivate or delete the maternal copy of the UBE3A gene. Most cases of Angelman syndrome occur when a segment of the maternal chromosome 15 containing this gene is deleted. In other cases, Angelman syndrome is caused by a mutation in the maternal copy of the UBE3A gene.[1]

In a small percentage of cases, a person with Angelman syndrome inherits two copies of chromosome 15 from his or her father, instead of one copy from each parent. This is called paternal uniparental disomy. Rarely, Angelman syndrome can also be caused by a chromosomal rearrangement called a translocation, or by a mutation or other defect in the region of DNA that controls activation of the UBE3A gene. These genetic changes can abnormally turn off (inactivate) UBE3A or other genes on the maternal copy of chromosome 15.[1]

The cause of Angelman syndrome is unknown in 10 to 15 percent of affected individuals. Changes involving other genes or chromosomes may be responsible for the condition in these individuals.[1]
Last updated: 6/13/2011

How might Angelman syndrome be inherited?

Most cases of Angelman syndrome are not inherited, particularly those caused by a deletion in the maternal chromosome 15 or by paternal uniparental disomy. These genetic changes occur as random events during the formation of reproductive cells (eggs and sperm) or in early embryonic development. Affected people typically have no history of the disorder in their family.[1]

Rarely, a genetic change responsible for Angelman syndrome can be inherited. For example, it is possible for a mutation in the UBE3A gene or in the nearby region of DNA that controls gene activation to be passed from one generation to the next.[1]
Last updated: 6/13/2011

References
  1. Angelman syndrome. Genetics Home Reference. July 2009; http://ghr.nlm.nih.gov/condition=angelmansyndrome. Accessed 6/13/2011.


Other Names for this Disease
  • AS
  • Happy puppet syndrome (formerly)
See Disclaimer regarding information on this site. Some links on this page may take you to organizations outside of the National Institutes of Health.