What causes Angelman syndrome?

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.