What are the symptoms of Angelman syndrome?
Angelman syndrome has several different symptoms, or characteristics, and they vary from person to person and with age.
Common symptoms of Angelman syndrome
Most people with Angelman syndrome (approximately 80% to 99%) have the following symptoms throughout their lives:
- Delayed development.
- Learning disabilities.
- Speech development issues, ranging from not speaking at all (being nonverbal) to only using a few words.
- Walking difficulties, such as clumsiness and a wide-based walk (gait).
- Ataxia (impaired balance or coordination).
- Seizures.
Facial features of Angelman syndrome
Common facial features of Angelman syndrome include:
- A short and broad skull (brachycephaly).
- Abnormally large tongue (macroglossia) that may stick out of their mouth.
- Abnormally small head (microcephaly).
- A big lower jaw (mandibular prognathia).
- Wide mouth.
- Widely spaced teeth.
Symptoms of Angelman syndrome specific to children
Children with Angelman syndrome typically have distinctive behaviors (in addition to the characteristic symptoms), including:
- A happy, excitable attitude.
- Frequent smiling and laughing.
- Frequent hand-flapping motions.
- Hyperactivity and a short attention span.
- Difficulty sleeping and needing less sleep than other children.
- A fascination with water.
With age, people with Angelman syndrome become less excitable, and their sleeping problems tend to improve.
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What causes Angelman syndrome?
Many of the characteristic symptoms of Angelman syndrome result from the loss of function of a gene called UBE3A. These changes occur early in fetal development before a baby is born.
A genetic mutation is a change in a sequence of your DNA. Your DNA sequence gives your cells the information they need to perform their functions. If part of your DNA sequence isn’t complete or is damaged, you might experience symptoms of a genetic condition.
People normally inherit one copy of the UBE3A gene from each biological parent. Both copies of this gene are “turned on” (active) in many of your body's tissues. But in certain areas of your brain, only the copy inherited from your birthing parent (maternal copy) is active.
If the maternal copy of the UBE3A gene is lost because of a chromosomal change or a gene mutation, you’ll have no active copies of the gene in some parts of your brain. This causes the characteristic symptoms of Angelman syndrome, a neurodevelopmental condition.
A person may have Angelman syndrome symptoms because parts of the UBE3A gene are inactive or missing (about 70% of cases). Structural changes to UBE3A may also result in Angelman syndrome (about 11% of cases).
Abnormalities of the UBE3A gene usually occur spontaneously (randomly), meaning they aren’t inherited (passed down). In a small number of cases, children don’t inherit a normal copy of chromosome 15 from their birthing parent (for example, they could inherit two copies of chromosome 15 from their other biological parent), leading to the development of Angelman syndrome.
In about 10% to 15% of cases, healthcare providers can’t determine the cause of Angelman syndrome. Changes involving other genes or chromosomes may be responsible for the condition in these cases.
