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Angelman syndrome - Introduction

NHS Choices Medical Reference

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Angelman syndrome is a rare genetic condition that affects approximately 1 in 25,000 people. It affects the nervous system,

causing severe physical and intellectual disability, with symptoms becoming noticeable from early childhood.

In most cases of Angelman syndrome, the genetic abnormality responsible for the disorder happens by chance around the time of conception. This means the disorder is not usually inherited.

There are, however, a few families where the condition is inherited and brothers and sisters may be affected.

Most children with Angelman syndrome are diagnosed between the ages of 18 months and 6 years, when the typical physical and behavioural symptoms are noticed. A blood test can be carried out to look for one of the genetic abnormalities that cause Angelman syndrome.

What are the symptoms?

A child with Angelman syndrome will have the following signs and symptoms:

  • a severe delay in development from 6-12 months
  • speech problems (most children do not speak or only say a few words)
  • movement or balance problems - usually ataxia (loss of co-ordination) and jerky movements of the limbs

A child with Angelman syndrome will also display distinctive behaviours, these may include:

  • frequent laughter and smiling, with little stimulus
  • being easily excitable, often flapping the hands
  • being restless
  • having a short attention span

Many children with Angelman syndrome will have an abnormally small head by the age of two, and many will develop seizures around this age.

Some children with Angelman syndrome will also have the following features and behaviours:

  • a flattened skull at the back
  • a tendency to stick out the tongue
  • feeding problems during infancy
  • a prominent chin
  • a wide mouth and wide-spaced teeth
  • frequent drooling
  • excessive chewing
  • the eyes looking in different directions (strabismus)
  • pale skin and light hair and eye colour
  • uplifted bent arms, especially during walking
  • increased sensitivity to heat
  • disturbed sleep, and needing less sleep than usual
  • attraction to, or fascination with, water
  • the spine bending abnormally to the left or right side (known as scoliosis)

What causes Angelman syndrome?

Many of the typical features of Angelman syndrome happen because the gene called UBE3A on chromosome number 15 is not functioning in the normal way.

Normally, people inherit one copy of the UBE3A gene from each parent and both copies are turned on (active) in most of the body's tissues. However, in certain areas of the brain, only the gene inherited from the mother is active.

In most cases of Angelman syndrome, the child's maternal copy of the UBE3A gene is not functioning normally or is missing altogether. This means the child does not have any active copies of the UBE3A gene in their brain.

There are several ways in which the activity (expression) of the UBE3A gene can be altered. These changes to the DNA usually occur by chance around the time of conception. However, rarely, there is a family history of the syndrome - so it's possible for the UBE3A alteration to be inherited and for several family members to be affected.

In some cases of suspected Angelman syndrome, the cause is unknown. In these individuals, it's important to rule out the possibility of other genetic conditions similar to Angelman syndrome.

How is it managed?

There is no cure for Angelman syndrome and some of the symptoms can be difficult to manage. You are likely to need help from a wide range of different health professionals.

Your child may benefit from some of the following treatments and aids:

  • Anti-epileptic medicine to control the seizures - sodium valproate, clonazepam and ethosuccimide are some of the drugs in common use.
  • Physiotherapy, attention to their sitting posture, a back brace and possibly spinal surgery to prevent their spine from curving further (read more about treating scoliosis). 
  • A feeding tube and other feeding aids, especially in infancy. In older children, weight gain may be a problem.
  • Occupational therapy to help them develop skills needed for dressing, feeding and other daily living activities.
  • An ankle foot orthosis (lower leg brace) to help them walk independently.
  • Picture boards, eye gaze technology and other visual aids to help them communicate.

Read more about caring for a disabled child and the aids and adaptations you may need if you're a parent carer.

Therapeutic horseriding, swimming, hydrotherapy and music therapy have been reported to be beneficial. Ask your healthcare team where you can access these therapies.

Outlook

With age, people with Angelman syndrome become less hyperactive and the sleeping problems tend to improve, although their frequent smiling persists.

People with Angelman syndrome will have a near-normal life expectancy, but will need looking after throughout their lives.

As a parent carer, it's important that you look after your own health and wellbeing too. The box on the left of this page provides links to further information that may help you.

Medical Review: August 20, 2012
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