About Angelman Syndrome
Traits & Symptoms
Early Signs of Angelman Syndrome in Babies
Angelman syndrome symptoms in babies typically become noticeable within the first year of life. While pregnancy, birth, and the newborn period are usually unremarkable, developmental delays typically start by 6 to 12 months of age, leading caregivers to seek further evaluation.
Most Infants Living with Angelman Syndrome Have:
Typical pregnancy and birth history
Normal birth weight and size
No major birth defects
Delayed developmental milestones (e.g., sitting, crawling, babbling)
Other common Angelman syndrome symptoms in babies are:
Low muscle tone (hypotonia)
Difficulty feeding (suck/swallow disorder, reflux)
Pale eye, skin, and hair color compared to family background (most often seen in those living with Deletion AS)
Signs and Symptoms of Angelman Syndrome in Children
As children grow, additional symptoms and physical characteristics of Angelman syndrome may become more apparent.
Common Neurological and Developmental Symptoms:
Severe speech impairment (limited or no use of words)
Receptive language (understanding what is said) and nonverbal communication (using other methods to communicate such as gestures) abilities that are often better than their speaking ability
Movement and balance difficulties (ataxia), resulting in difficulties walking and using their hands
Unique behaviors, including frequent laughter and smiling, an apparently happy demeanor, and excitability
Hyperactivity and short attention span
Seizures, typically starting before age 3
Difficulty sleeping, including abnormal sleep-wake cycles and frequent nighttime awakenings
Fascination with water
Common Physical Characteristics of Angelman Syndrome:
Small head size for the body size (microcephaly)
Strabismus (eye crossing), lazy eye, or other vision problems
Scoliosis (curving of the spine) and orthopedic concerns
Constipation and gastrointestinal issues
Common Angelman Syndrome Symptoms in Adults
While individuals living with AS continue to experience developmental and physical challenges into adulthood, symptoms may evolve over time. Some common Angelman syndrome symptoms in adults include:
Improved hyperactivity but persistent movement difficulties
Continued need for assistance with daily activities
Nonverbal or limited verbal communication
Ongoing sleep disturbances, though they may lessen with age
Seizures may improve but often require lifelong management
Increased risk of mobility issues, including joint problems and scoliosis progression
What Causes Angelman Syndrome?
Angelman syndrome is caused by genetic differences affecting chromosome 15, specifically the UBE3A gene. The UBE3A gene codes for the UBE3A protein, which is essential for brain development and function. In individuals living with AS, this gene is either missing, mutated, or silenced, leading to an absence of functional UBE3A protein in the brain, which causes the neurological symptoms of Angelman syndrome. The different genetic mechanisms that cause AS are called genotypes.
Deletion
Mutation
Uniparental Disomy (UPD)
Imprinting Center Defect (ICD)
Mosaic
Diagnosing Angelman Syndrome
If you suspect a loved one may live with AS, consulting a healthcare provider is essential. Since AS symptoms overlap with other conditions, genetic testing is necessary for an accurate diagnosis. Genetic testing for AS is complicated. Because there are different genetic mechanisms that cause AS, there are currently multiple genetic tests required to confirm or rule out the diagnosis.
The first step towards diagnosis is to talk with your child’s primary care provider.
A primary care provider may note developmental delays and refer to a specialist for further assessments. In some cases, a primary care provider may order genetic testing.
Because genetic testing for Angelman syndrome is complex and may not be routinely performed by primary care doctors, consulting a specialist such as a neurologist or geneticist is often recommended. In the USA, insurance pre-authorization is often required for genetic testing and is typically performed by specialists.
When Should You Seek Genetic Testing?
The most common symptom prompting Angelman syndrome diagnosis in babies is developmental delay, but many conditions or health issues can cause delays. Some primary care providers may take a “wait and see” approach, monitoring for additional symptoms before ordering genetic tests or referring to a specialist. You know your child best. If you have concerns, discuss those concerns with your child’s medical team.
For families in the United States, Project FIND-OUT offers free genetic testing and counseling for infants aged 3 to 12 months who meet specific criteria including developmental delays. This testing is not specific to AS but may identify some AS genotypes. Learn more at Project FIND-OUT
Conclusion
Angelman syndrome is a complex disorder with physical and behavioral characteristics that evolve over a lifetime. While symptoms may vary in severity, early recognition of Angelman syndrome symptoms can lead to prompt diagnosis.
A confirmed diagnosis can have many benefits:
Directing early interventions, like physical and speech therapy
Facilitating appropriate Angelman syndrome-specific medical management and screening. For more information, see the AS care consensus statement.
Enabling participation in clinical trials and research
Connecting you to a community of support, empowerment, and hope
If you suspect a loved one may live with AS, talking to your loved one’s medical providers, seeking specialist consultation and genetic testing are the best next steps toward diagnosis and management.