About Angelman Syndrome

What is Angelman Syndrome?

Angelman syndrome (AS) is a rare neurogenetic disorder that affects approximately one in 15,000 people – approximately 500,000 individuals worldwide. Children and adults with AS typically have balance issues, motor impairment and can have debilitating seizures. Some individuals never walk. Most do not speak. Disruptive sleep also can be a serious challenge to the individual and caretaker(s).

Individuals with AS require continuous care and are unable to live independently. They have a normal life expectancy. This is life today for people living with Angelman syndrome, but hope is here. Scientists believe that AS has the greatest potential for being cured when compared to any other neurogenetic disorder, and FAST has a plan well underway to achieve just that.

what is angelman syndrome
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Typical characteristics of AS are not usually evident at birth. Individuals with this disorder may have feeding difficulties as infants and noticeable delayed development around 6-12 months of age. They need intensive therapies to help develop functional skills. AS affects every race and both genders. It is often misdiagnosed as autism or cerebral palsy.

Behavioral Traits

People with Angelman syndrome often have unique behavioral characteristics, including a happy demeanor, characterized by frequent laughing, smiling and excitability. Many individuals with AS have an affinity for water and take great pleasure in water-based activities like swimming and bathing. It is important to note that Angelman syndrome is a spectrum disorder and as such, not all individuals exhibit the same behavioral characteristics or preferences.

Tests & Diagnosis

Learn about the criteria that doctors use to determine if an individual has Angelman syndrome, and read about available tests and common misdiagnoses.


There are different types of testing to determine if your child has Angelman syndrome. We provide information for parents and individuals that do not have a working knowledge of genetics but would like to understand what tests are available and what they mean.



The journey to Angelman syndrome diagnosis is not always easy. There is not a definitive age when diagnosis is made, but thanks to scientific advancements and diligent infant screenings, diagnosis is occurring earlier and sooner. The presentation of Angelman syndrome varies by individual and genotype.

Testing Pathway to Diagnosis

This algorithm guides you and your provider through comprehensive genetic testing for Angelman syndrome. You can also press start and further your understanding of Angelman syndrome genotypes or figure out the next step in genetic testing.

Causes of Angelman Syndrome

Angelman syndrome is a single-gene disorder caused by a loss of function in the UBE3A gene on the maternal 15th chromosome. People have two sets of chromosomes – one inherited from the mother and one from the father. In a typical person, the maternally inherited UBE3A gene is active, while the copy of the gene inherited from the father is silenced in the neurons in our brains – a phenomenon known as imprinting. For people with AS, this maternal gene is not doing its job, and that impacts their Messenger RNA (mRNA).
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What is mRNA?

mRNA is the FedEx of the body. Our DNA uses mRNA as a delivery service to send blueprints to the protein-assembly factories of our cells. People with AS have a mutation, deletion or other defect in their UBE3A gene that interrupts this delivery service. As a result, their neurons do not make any functional UBE3A protein, and that’s what triggers the symptoms of AS. This protein is what helps us walk, talk and perform other everyday tasks.


Is it Genetic?

In most cases, Angelman syndrome isn’t inherited – particularly those caused by a deletion or UPD. Instead, these genetic changes occur as random events during the formation of reproductive cells or in early embryonic development.

Types of Angelman Syndrome

All conditions of Angelman syndrome involve a disruption to the UBE3A gene on the maternal 15th chromosome. Different tests are required to determine the specific genotype: Deletion, Mutation (UBE3A), Uniparental Disomy (UPD), or Imprinting Defect (ICD). More information about those tests is available here. FAST is aggressively pursuing therapeutic strategies for all genotypes.
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In typical individuals, UBE3A is expressed from both the paternal (blue) and maternal (magenta) chromosomes 15 in most tissues. In neurons, the paternal UBE3A allele is silenced by the process of genomic imprinting. As a result, only the maternal UBE3A allele is expressed in neurons from typical individuals.



DNA (deoxyribonucleic acid) is the main component of chromosomes. It contains our unique genetic code. Most individuals with AS are missing a piece of DNA in region 15q11‑13 on the maternal chromosome 15.


This occurs when there is a small abnormality in the DNA of the UBE3A gene. A mutation can happen anywhere on the gene.

Uniparental Disomy(3-7%)

An individual with UPD has two copies of chromosome 15 from their father, instead of one each from the father and mother.
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Imprinting Defect(<3%)

The imprinting center is a small stretch of DNA located in the q11-13 region of the chromosome. In rare cases, the mother’s chromosome 15 is blank, and the center copies the father’s chromosome 15. This is an imprinting defect.


Genetic mosaicism is an extremely rare genotype of Angelman syndrome where a small proportion of the body’s cells are expressing UBE3A. A person with mosaicism has a mixture of fully expressing and non-expressing UBE3A DNA in the cells of the body. Most reported cases have an estimated 5-20% of cells that have maternal expression, though between 1-40% are reported.

Newly Diagnosed?

Welcome to an amazing community that you never wanted to be part of.

As you begin your journey through the diagnosis of your loved one, please know that we are here for you with resources and community support, when you are ready.

Until then, we invite you to explore the information below. We are standing by to answer your questions!

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Unfortunately, epilepsy is common in individuals with Angelman syndrome (AS). Approximately 85% of individuals with AS will experience seizures within the first three years of their life, although seizures in AS can present at any age. The good news is that there are multiple, effective treatment options for managing seizures in patients with AS including anti-epileptic medications, therapeutic dietary intervention and vagal nerve stimulator (VNS) implant.

Whether you are newly diagnosed, or have been on this journey for years, being able to recognize a seizure, properly communicate symptoms to your child’s medical provider, and knowing best practices for treating seizures in AS will be your best defense in ensuring the safety and health of your child.

Please take the time to watch this very descriptive and informative video on seizures in AS.
Individuals with AS can present with different types of seizures including:
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If your child has recently received the diagnosis of AS, speak to your medical provider about adding a neurologist to your medical team, scheduling a baseline EEG (electroencephalogram) and creating a Seizure Action Plan so you are informed and prepared in the event your child develops epilepsy.

For emergency seizure support, we encourage families and providers to reach out to the Epilepsy and Seizures 24/7 helpline through the Epilepsy Foundation for high-quality care for your loved one.   

Helpful Resources

As diverse as our Angelman community is, we are all united in one goal: a better future for our children. FAST is committed to bringing life-changing treatments to all individuals with Angelman syndrome, but we need your help!
As diverse as our Angelman community is, we are all united in one goal: a better future for our children. FAST is committed to bringing life-changing treatments to all individuals with Angelman syndrome, but we need your help!
FAST is the driving force behind research for a cure. FAST’s Roadmap to a Cure outlines the various strategies to treat Angelman syndrome. These approaches, which have already been tested in animal models, are believed to have the potential to reverse the effects of the disorder in children, teens and adults.
Educating our community, family, and friends about Angelman syndrome is an important responsibility. Let’s make raising awareness and funds easy and fun! You’re invited to create a custom AS Fact Card.