The following information may help to address your question:
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] Treatment is aimed at addressing each individual's symptoms and may include antiepileptics for
seizures; physical, occupational, and speech therapy; and special education services.
[2]
Last updated: 12/31/2015
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: 3/31/2016
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. In these instances, 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: 3/31/2016
After having one child with Angelman syndrome, what is the chance that future children will inherit it as well?
Although most cases of Angelman syndrome are not inherited, particularly those caused by a deletion in the maternal chromosome 15, the risk of having another child with Angelman syndrome depends on the specific cause. You will need to speak with a genetics professional to understand the risk in future pregnancies that are specific to your situation.
Last updated: 3/31/2016
Is there any way to avoid having a child with Angelman syndrome in a future pregnancy?
There are a number of genetic tests that can be used to inform a couple about the possible outcomes of a current or future pregnancy. Examples of two such tests are
prenatal diagnosis and
preimplantation genetic diagnosis (PGD).
[3]
Prenatal diagnosis can be used to diagnose a condition in a developing fetus. If the underlying genetic cause of a disorder in a family is known, testing can be completed to analyze the genetic material of the fetus. This is typically completed around 10-13 weeks' gestation via chorionic villus sampling or around 15+ weeks' gestation via amniocentesis. Prenatal diagnosis may help parents prepare emotionally for the birth and to plan the delivery with their health care providers. Parents can also use this information to make decisions regarding whether or not to continue the pregnancy.[3][2]
PGD is an alternative to prenatal diagnosis. It is used following in vitro fertilization to diagnose a genetic disease or condition in embryos. Only embryos that do not carry the disease-causing mutation are implanted in the mother's womb. PGD allows testing to occur before a pregnancy begins. In many cases, the disease-causing mutation must be identified in an affected parent before PGD or prenatal diagnosis can be performed.[3]
Last updated: 3/31/2016
How can I find a genetics professional in my area?
Last updated: 12/6/2017
We hope this information is helpful. We strongly recommend you discuss this information with your doctor. If you still have questions, please
contact us.
Warm regards,
GARD Information Specialist
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