Angelman Syndrome

Definition of Angelman Syndrome

Angelman syndrome is a complex genetic disorder that affects the central nervous system and causes severe physical and learning disabilities. Many of the characteristic features of Angelman syndrome result from the loss of function of a gene called UBE3A on chromosome 15 due to inactivation or mutation of the gene.

Causes of Angelman Syndrome

Angelman syndrome is caused by the absence or loss of function of a gene called UBE3A on chromosome 15. This impacts brain functioning, which results in a range of symptoms. Sometimes the causes of Angelman syndrome is unknown.

Types of Angelman Syndrome

1. Deletion positive – this is the most common  type of this syndrome affecting about 70% of cases of AS and occurs when the mother’s copy of UBE3A has been deleted and is not present.
2. Mutation – this type affects about 11% of cases of AS and occurs when there is a mutation or alteration in the chromosome 15 inherited from the mother. This mutation or alteration either prevents the expression of UBE3A or alters its function.
3. Imprinting Center Defect – this affects about 6% of cases of AS and occurs when there is an abnormality in the imprinting center of the chromosome 15 inherited from the mother. The imprinting center is the area of the chromosome that controls whether genes are turned on or off. So, even though UBE3A from the mother may be present, the problem in the imprinting center makes the UBE3A gene unavailable to the brain.
4. Paternal Uniparental Disomy (UPD) – this affects about 3% of cases of AS and occurs when there are two chromosome 15 from the father, but none from the mother. Since the UBE3A from the father is silenced or turned off, and the one from the mother is absent, the brain cannot get the information it needs from UBE3A.

(APA, 2020; Dagli et al, 2021; Morris & Morris, 1998)

Symptoms of Angelman Syndrome

Those affected by this syndrome usually begging to show signs of delayed development around the age of 6 to 12 months. Each individual with Angelman syndrome is unique, so they may have one or more of the following symptoms: 

• Frequent laughter and smiling.
• Easily excitable, often expressed through hand flapping or walking with arms in the air.
• Jerky body movements.
• Tremors.
• Delays in motor development.
• Problems with movement and balance.
• Little or no speech.
• Mouthing of objects.
• Short attention span.
• Hyperactivity. 
• Feeding difficulties.
• Sleep problems and a need for less sleep. 
• Tongue thrusting.
• Crossed eyes (Strabismus).
• Small head size with flatness in the back of the head.
• A lower jaw that juts out.
• Light pigmentation in the hair skin and eyes.
• Delayed development such as being unable to sit unsupported or making babbling sounds/noises.
• Severe communication impairment.
• Intellectual disability.
• Seizure disorders usually starting before the age of 3 years.

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References

American Psychological Association (2020). Angelman Syndrome.

Dagli, A. I., Mathews, J., & Williams C. A. (2021). Angelman Syndrome. National Center for Biotechnology Information.

Morris, R. J., & Morris, Y. P. (1998). Angelman syndrome. In L. Phelps (Ed.), Health-related disorders in children and adolescents: A guidebook for understanding and educating (pp. 50–55). American Psychological Association.