Angelman syndrome is a rare genetic condition that affects the nervous system and causes severe physical and learning disabilities.

A person with Angelman syndrome will have a near-normal life expectancy, but they will need support throughout their life.

Characteristics of Angelman syndrome

A child with Angelman syndrome will begin to show signs of delayed development at around 6 to 12 months of age, such as being unable to sit unsupported or make babbling noises.

Later, they may not speak at all or may only be able to say a few words. However, most children with Angelman syndrome will be able to communicate using gestures, signs or other systems.

The movement of a child with Angelman syndrome will also be affected. They may have difficulty walking because of issues with balance and co-ordination (ataxia). Their arms may tremble or make jerky movements, and their legs may be stiff.

Several distinctive behaviours are associated with Angelman syndrome, although a child with the condition may not have all of these behaviours. They include:

• frequent laughter and smiling, often with little stimulus
• being easily excitable, often flapping the hands
• being restless (hyperactive)
• having a short attention span
• trouble sleeping and needing less sleep than other children
• a particular fascination with water

By around 2 years of age, a small head which may also be flat at the back (microbrachycephaly) may be noticeable in some children with Angelman syndrome. Children with Angelman syndrome may also start to have seizures or fits around this age.

Other possible features of the syndrome include:

• tendency to stick the tongue out
• crossed eyes (strabismus)
• skin, hair and eyes that are paler than other family members
• a wide mouth with widely spaced teeth
• a side-to-side curvature of the spine (scoliosis)
• walking with arms in the air

Some young babies with Angelman syndrome may have difficulties feeding because they're unable to co-ordinate sucking and swallowing. In such cases, they may need to be fed through a feeding tube. Babies with Angelman syndrome may need to be treated for reflux.

Causes of Angelman syndrome

In most cases of Angelman syndrome, the child's parents do not have the condition and the genetic difference responsible for the syndrome happens by chance around the time of conception.

Angelman syndrome usually happens when the gene known as UBE3A is either missing or not working properly. A gene is a single unit of genetic material (DNA) that acts as an instruction for the way an individual is made and develops.

Usually a child gets 2 copies of this gene, one from each parent, but only the gene from the mother is active.

Most cases of Angelman syndrome are caused by the child not getting a copy of the UBE3A gene from its mother, or the gene not working. This means there's no active copy of the gene in the child's brain.

In a small number of cases, Angelman syndrome happens when a child gets 2 inactive copies of the gene from their father, rather than 1 from each parent.

Sometimes the cause of Angelman syndrome is unknown. Most children in these unexplained cases have different conditions involving other genes or chromosomes.

Diagnosing Angelman syndrome

Angelman syndrome may be suspected if a child's development is delayed and they have the syndrome's distinctive characteristics.

A blood test is used to confirm the diagnosis. Several genetic tests will be done on the blood sample. These tests look for:

• any chromosomes or pieces of chromosomes that are missing
• changes in the mother's or father's UBE3A gene that they may have passed on
• changes in the child's UBE3A gene that would stop it from working

For each child with Angelman syndrome, it's important to know the genetic change that caused the condition. This helps to determine your chance of having another child with Angelman syndrome.

Most children with Angelman syndrome are diagnosed between the ages of 9 months to 6 years, when physical and behavioural symptoms become apparent.

If your child is diagnosed with Angelman syndrome, you will be able to talk to a genetic doctor about what support they might need.

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