Angelman Syndrome

Condition 101

What is the definition of Angelman Syndrome?

Angelman syndrome (AS) is a genetic condition that causes problems with the way a child's body and brain develop. The syndrome is present from birth (congenital). However, it often isn't diagnosed until about 6 to 12 months of age. This is when development problems are first noticed in most cases.

What are the causes for Angelman Syndrome?

This condition involves the gene UBE3A.

Most genes come in pairs. Children receive one from each parent. In most cases, both genes are active. This means information from both genes is used by the cells. With the UBE3A gene, both parents pass it on, but only the gene passed on from the mother is active.

Angelman syndrome most often occurs because UBE3A passed on from the mother doesn't work the way it should. In some cases, AS is caused when two copies of UBE3A gene come from the father, and none come from the mother. This means neither gene is active, because they both come from the father.

What are the symptoms for Angelman Syndrome?

In newborns and infants:

  • Loss of muscle tone (floppiness)
  • Trouble feeding
  • Heartburn (acid reflux)
  • Trembling arm and leg movements

In toddlers and older children:

  • Unstable or jerky walking
  • Little or no speech
  • Happy, excitable personality
  • Laughing and smiling often
  • Light hair, skin, and eye color compared to rest of family
  • Small head size compared to body, flattened back of head
  • Severe intellectual disability
  • Seizures
  • Excessive movement of the hands and limbs
  • Sleep problems
  • Tongue thrusting, drooling
  • Unusual chewing and mouthing movements
  • Crossed eyes
  • Walking with arms uplifted and hands waving

Most children with this disorder don't show symptoms until about 6 to 12 months. This is when parents may notice a delay in their child's development, such as not crawling or starting to talk.

Children between 2 and 5 years of age start to show symptoms such as jerky walking, happy personality, laughing often, no speech, and intellectual problems.

What are the current treatments for Angelman Syndrome?

There is no cure for Angelman syndrome. Treatment helps to manage health and development problems caused by the condition.

  • Anticonvulsant medicines help control seizures
  • Behavior therapy helps manage hyperactivity, sleep problems, and development problems
  • Occupational and speech therapy manage speech problems and teach living skills
  • Physical therapy helps with walking and movement problems

What are the support groups for Angelman Syndrome?

Angelman Syndrome Foundation:


What is the outlook (prognosis) for Angelman Syndrome?

People with AS live close to a normal lifespan. Many have friendships and interact socially. Treatment helps improve function. People with AS can't live on their own. However, they may be able to learn certain tasks and live with others in a supervised setting.

What are the possible complications for Angelman Syndrome?

Complications may include:

  • Severe seizures
  • Gastroesophageal reflux (heartburn)
  • Scoliosis (curved spine)
  • Accidental injury due to uncontrolled movements

When should I contact a medical professional for Angelman Syndrome?

Call your health care provider if your child has symptoms of this condition.

How do I prevent Angelman Syndrome?

There is no way to prevent Angelman syndrome. If you have a child with AS or a family history of the condition, you may want to talk with your provider before becoming pregnant.


Dagli AI, Mueller J, Williams CA. Angelman syndrome. GeneReviews. Seattle, WA: University of Washington; 2015:5. PMID: 20301323 Updated December 27, 2017. Accessed August 1, 2019.

Kumar V, Abbas AK, Aster JC. Genetic and pediatric diseases. In: Kumar V, Abbas AK, Aster JC, eds. Robbins Basic Pathology. 10th ed. Philadelphia, PA: Elsevier; 2018:chap 7.

Madan-Khetarpal S, Arnold G. Genetic disorders and dysmorphic conditions. In: Zitelli BJ, McIntire SC, Nowalk AJ, eds. Zitelli and Davis' Atlas of Pediatric Physical Diagnosis. 7th ed. Philadelphia, PA: Elsevier; 2018:chap 1.

Nussbaum RL, McInnes RR, Willard HF. The chromosomal and genomic basis of disease: disorders of the autosomes and sex chromosomes. In: Nussbaum RL, McInnes RR, Willard HF, eds. Thompson & Thompson Genetics in Medicine. 8th ed. Philadelphia, PA: Elsevier; 2016:chap 6.

Latest Research

Latest Advance
  • Condition: Nonepileptic Myoclonus in Angelman Syndrome
  • Journal: Brain & development
  • Treatment Used: Perampanel
  • Number of Patients: 4
  • Published —
This study tested the effectiveness of perampanel for nonepileptic myoclonus in patients with Angelman syndrome.
Latest Advance
  • Condition: Sleep Disturbances in Angelman Syndrome
  • Journal: Journal of clinical sleep medicine : JCSM : official publication of the American Academy of Sleep Medicine
  • Treatment Used: Mirtazapine
  • Number of Patients: 8
  • Published —
This study tested the safety and efficacy of using mirtazapine to treat sleep disturbances in patients with Angelman syndrome.
Latest Advance
  • Condition: Angelman syndrome
  • Journal: Orphanet journal of rare diseases
  • Treatment Used: Minocycline
  • Number of Patients: 36
  • Published —
This study evaluated the efficacy and safety of minocycline in patients with Angelman syndrome.
Latest Advance
  • Condition: Non-Convulsive Status Epilepticus (NCSE) in Pediatric Patients with Angelman Syndrome
  • Journal: Epilepsy & behavior : E&B
  • Treatment Used: Diazepam
  • Number of Patients: 104
  • Published —
This study reported experience in pediatric patients with Angelman syndrome (genetic disorder; AS) and non-convulsive status epilepticus (constant seizures; NCSE) treated outpatient with a tapering course of oral diazepam.

Clinical Trials

Clinical Trial
  • Status: Active, not recruiting
  • Study Type: Drug
  • Participants: 20
  • Start Date: February 24, 2020
A Phase 1/2 Open-label, Multiple-dose, Dose-escalating Clinical Trial of the Safety and Tolerability of GTX-102 in Pediatric Patients With Angelman Syndrome (AS)
Clinical Trial
  • Status: Recruiting
  • Study Type: Procedure
  • Participants: 36
  • Start Date: December 18, 2019
A Study to Explore Cerebrospinal Fluid and Blood Biomarkers in Participants With Angelman Syndrome