What's Angelman syndrome?
Angelman syndrome (AS) is a neurodevelopmental disorder caused by loss of the maternal copy of the UBE3A gene in the brain, usually through a deletion in the chromosome 15 inherited from the mother (the 15q11-q13 region). It produces severe intellectual disability, absent speech, an unsteady (ataxic) gait, and epilepsy in most patients, along with a characteristically happy, excitable demeanor.
| Also indexed as | OMIM:105830, MONDO:0007113 |
|---|---|
| Features mapped | 20 |
| Treatments mapped | 3 |
| Published sources | 14 |
| Last reviewed | 2026-08-04 |
Signs and symptoms
Strabismus
Eye problems in Angelman syndrome are not yet fully understood. Researchers have had limited information about how well surgery for crossed eyes works and whether certain genetic changes are linked to specific eye findings because previous studies included relatively small numbers of patients.
Exotropia
Surgery to correct eye misalignment is generally effective in people with Angelman syndrome and produces lasting results regardless of the specific genetic subtype. The findings also suggest that monitoring vision based on a person’s genetic subtype may help identify vision problems earlier.
Myopia
Severe nearsightedness was observed only in patients who had a deletion-type genetic change, although it was found in just two individuals in this study.
Sleep-wake cycle disturbance
Disrupted sleep is common in angelman syndrome. Children with the condition can have some of the most severe and long-lasting sleep difficulties of any neurogenetic disorder.
Absent speech
Most people with AS have little or no spoken language. Communication usually relies on gestures, devices, and non-verbal means rather than speech.
Severe intellectual disability
Severe intellectual disability is a core feature of angelman syndrome. It typically occurs together with absent speech, an unsteady (ataxic) walk, and a characteristic pattern of behavior.
Ataxia
Ataxia is a lack of coordination that makes movement and balance unsteady. It is one of the recognized features of angelman syndrome.
Intellectual disability
Severe intellectual disability is a defining feature of AS, present in essentially all patients and shaping lifelong support needs.
Motor delay
Researchers described a boy who was nearly 4 years old and had a family history of autism and ADHD. He experienced delayed motor development, very low muscle tone, an unusually broad head shape, poor trunk control, difficult-to-treat seizures, and severe developmental delays that left him unable to walk or speak.
EEG abnormality
An EEG records the brain's electrical activity. In angelman syndrome the EEG often shows particular patterns, such as rhythmic delta activity, that go along with the epilepsy.
Global developmental delay
Global developmental delay means that development across many areas — movement, thinking, and communication — is slower than expected. It is one of the defining features of angelman syndrome.
Happy demeanor
A happy demeanor is part of the characteristic behavioral pattern of angelman syndrome. It often goes along with laughter that is easily set off, a short attention span, restless overactive movement, putting objects in the mouth, sleep problems, and a draw toward water.
Seizure
Seizures are common in angelman syndrome. The epilepsy often includes atypical absence seizures (brief lapses in awareness) and myoclonic seizures (sudden muscle jerks).
Hyperactivity
Hypermotoric behavior — being very active and restless — is one of the behavioral features of angelman syndrome, along with a short attention span.
Paroxysmal bursts of laughter
Frequent laughter that comes without an obvious reason is one of the characteristic behaviors of angelman syndrome, alongside a happy demeanor.
Sporadic
In sporadic ALS (a form of the disease that appears without a family history), the same kind of changes to how the NRG3 gene is processed occur as in inherited ALS caused by UBQLN2 mutations.
Brachycephaly
Researchers described a boy who was nearly 4 years old and had severe developmental challenges, including delayed movement skills, very low muscle tone, poor control of his upper body, difficult-to-treat seizures, and an inability to walk or speak. He also had a family history of autism and ADHD.
Hypotonia
This case involved a person with Angelman syndrome who was initially diagnosed with cerebral palsy. The individual had severe developmental delays, autism-like behaviors, low muscle tone, and epilepsy.
Generalized hypotonia
This case describes a person with Angelman syndrome who was first thought to have cerebral palsy. They experienced severe developmental delays, autism-like behaviors, low muscle tone, and seizures.
Hypopigmentation of the skin
Hypopigmentation — lighter skin, hair, or eye coloring — can be seen in angelman syndrome, alongside developmental delay, limited speech, and a happy demeanor.
How it is diagnosed
Angelman syndrome
Diagnosed using: Genetic testing.
“Genetic testing confirmed a deletion in the Prader-Willi/AS critical region on chromosome 15.”
Angelman syndrome
Diagnosed using: DNA methylation analysis of 15q11-q13.
“Standard-of-care testing involves SNRPN promoter methylation, microarray and genomic analyses for individuals presenting with these features.”
Angelman syndrome
Diagnosed using: UBE3A gene sequencing.
“Methylation Specific-Multiplex Ligation-Dependent Probe Amplification (MS-MLPA) of the 15q11.2-q13 region was carried out in our laboratory as the first diagnostic…”
Treatment and management
What the research describes, not a recommendation. Treatment decisions belong with your clinician.
This covers treatments that appear in the published research mapped here. Investigational and experimental therapies are not included, so their absence is a boundary of this map, not a sign they do not exist.
antiseizure medication
Seizures in angelman syndrome are managed with antiseizure medication. Levetiracetam and clobazam are currently the favored first-line choices; valproate and clonazepam also work but have a more complicated side-effect profile.
Used to help with: Angelman syndrome.
“Levetiracetam and clobazam are currently the favored first-line agents; valproate and clonazepam are efficacious but carry a more complex adverse-effect profile.”
ketogenic diet
For seizures in angelman syndrome that do not respond to medication, dietary approaches such as the ketogenic diet and the low glycemic index diet can be added as extra options.
Used to help with: Angelman syndrome.
“The ketogenic and low hypoglycemic index diets offer adjunctive options for refractory cases.”
behavioral sleep intervention
For the sleep problems of angelman syndrome, non-drug behavioral strategies can help. The most effective involve keeping a consistent bedtime routine, gradually shifting the sleep schedule, and coaching parents to manage sleep behaviors.
Used to help with: Angelman syndrome.
“The most effective approaches involved establishing consistent bedtime routines, gradually adjusting sleep schedules, and coaching parents to manage sleep behaviors.”
What changes how it shows up
Carrying the genetic change is not the whole story. The factors below are described in the research mapped here as changing whether, or how strongly, the condition appears. They modulate how the genotype is expressed; they do not, on their own, cause or cure it.
maternal UBE3A loss at 15q11-q13
Angelman syndrome is an imprinting condition: it is caused by loss of the working copy of the UBE3A gene inherited from the mother, in the 15q11-q13 region of chromosome 15. Because the paternal copy of UBE3A is normally switched off in the brain, losing the maternal copy leaves no active gene.
Described as modulating: Angelman syndrome.
“The AS is an imprinting genomic disease characterized by the loss of function of the maternal UBE3A gene, located in the 15q11-q13.”
molecular mechanisms of UBE3A loss
The loss of UBE3A function in angelman syndrome can happen in several ways: a deletion of the 15q11.2-q13 region, a change within the UBE3A gene itself, inheriting both copies of chromosome 15 from the father (paternal uniparental disomy), or a defect in the imprinting that controls which copy is active.
Described as modulating: Angelman syndrome.
“Functional loss of UBE3A is due to 15q11.2-q13 deletion, mutations in the UBE3A gene, paternal uniparental disomy and genomic imprinting defects.”
How to read the evidence labels
Where this comes from
This guide is built from 14 published source(s). Every claim above links back to one of them. Click any source ID to read the original on PubMed.
Take it further
Printed, source-linked documents built from this condition's graph — ready to bring to an appointment or attach to a coverage request. Every claim carries its published source, the same as this guide.