Angelman syndrome (AS) is a rare neurogenetic disorder affecting at least 1 in every 15,000 people, or 500,000 worldwide. AS is often first detected between 6 and 12 months of age, when an infant shows delays in maturing—for example not yet crawling or babbling. Individuals affected by AS experience delayed physical development, mental disability, problems with speech and balance, limited motor skills, and sometimes seizures.

people have Angelman syndrome
the average age when developmental delays first become apparent
the average age for the onset of seizures
Human cells contain genes from both biological parents, which are encoded in 23 pairs of chromosomes. Chromosomes are structures made of proteins and DNA, and they provide the genetic blueprint each individual needs to grow and develop. Each chromosome has genes from the person’s mother (referred to as the maternal copy) and father (the paternal copy). Angelman syndrome is caused by the maternal copy of chromosome 15 being missing or damaged, particularly the gene UBE3A that produces a protein of the same name. This protein is used to help with brain development, and a deficiency of it can lead to a diagnosis of AS.
It is still unknown why a person might have missing or damaged maternal copy in the genetic structure in chromosome 15, and accordingly, there are few identifiable risk factors for developing Angelman syndrome. A person can develop AS with no family history of the disorder. However, having a family history of the disease can increase an infant’s risk for AS.
Angelman syndrome symptoms vary in severity. The earliest symptoms of Angelman syndrome include developmental delays in infancy, including no crawling or babbling at 6 to 12 months. From then on, symptoms include trouble sucking or feeding; trouble going to sleep or staying asleep; being easy to excite; mental disability; no speech or very little speech; trouble walking, moving, or balancing; stiff or jerky movements; crossed eyes; lighter than expected color of hair, skin, and eyes; and unusual behaviors, such as flapping the hands, lifting up arms while walking, and thrusting out the tongue. Head size may be smaller than average by age 2, and seizures may occur starting between 2 and 3 years of age. Children with AS may be hyperactive—though this lessens over time—and over time, they are more likely to develop obesity or scoliosis (curved spine). By adulthood, many of those with AS are still unable to walk or speak. However, most people with AS have a tendency to smile and laugh often, and outwardly they may appear happier than the average person.
AS is usually not noticeable at birth. Parents who observe that their child isn’t developing typical motor skills within 6 to 12 months should discuss it with their doctor, who may be able to diagnose the condition at that time. But it is important to keep in mind that delayed development isn’t necessarily a sign of a disorder or future disability. Children naturally develop at different rates.
Because AS is a genetic disease, proper diagnosis relies on genetic testing. There are a variety of genetic testing methods to determine if a person has AS, and the field has evolved quite a bit over the last few decades. The Foundation for Angelman Syndrome Therapeutics (FAST), the leading advocacy group for finding a cure for the disorder, has detailed information about genetic testing for AS.
There is currently no cure for AS, though several research efforts are in progress. Anticonvulsant medications can be used to treat seizures. AS is not a degenerative disease, and while the condition certainly presents many challenges, those affected by it tend to have nearly typical lifespans. People with AS cannot live independently, and usually they require continuous care.
The Foundation for Angelman Syndrome Therapeutics (FAST) believes that AS is now the neurogenetic disorder with the greatest potential to be cured. The disorder is monogenic, meaning that it is only related to one specific gene, as opposed to multiple possible genes. This allows for very focused research. The organization outlines four “pillars” of a drug–development pipeline—in other words, four different approaches in active stages of research. These approaches explore different potential ways to make up for the missing or damaged maternal copy of the UBE3A gene. The development of CRISPR technology for gene editing is also promising as a potential part of finding a cure. The large amount of data and details FAST provides indicate that the progress being made to find a cure is substantial.
New to research? Read our guide, How to Read a Research Study, to learn some tips for reading scientific publications and interpreting results.
Mayo Clinic: Angelman Syndrome
FAST: The Foundation for Angelman Syndrome Therapeutics

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