Angelman syndrome Dr Trisha Macnair Angelman syndrome is a rare condition characterised by severe learning difficulties and unsteady or jerky movements.

In this article

What causes it? What are the symptoms?

How is it diagnosed? What's the treatment?

Angelman syndrome is a chromosomal disorder caused by the absence of a gene. Interestingly, 75 per cent of those with Angelman syndrome have a similar genetic fault to that found in another genetic condition, Prader-Willi syndrome, but occurring on the chromosome 15 inherited from the mother rather than the father.

The genetic abnormality may be due to one of several possible types of problems with the chromosomes:

• A small deletion of part of chromosome 15 - this accounts for about 75 per cent of cases
• Paternal disomy - about two to three per cent of cases result from inheriting two copies of chromosome 15 from the father
• Mutation of the UBE3A gene in 15 per cent - there's a risk the condition will recur in other children born to the mother
• Translocation involving chromosome 15 in a few cases
• An error in the imprinting of chromosome 15 in about five per cent
• In some cases, the genetic abnormality has yet to be identified

Chromosome 15 is almost unique in that it carries an imprinted region, which means that it's marked so the copy inherited from the mother behaves differently from that from the father. Errors in imprinting can affect a baby's development. In this type of Angelman syndrome, there's a risk the condition will recur in other children born to the mother.

Typical features of Angelman syndrome are a small head (microcephaly), epilepsy, severe learning difficulties (with poor communication skills and little or absent speech), an unsteady or ataxic gait, a characteristic facial appearance and a happy disposition.

Early developmental delay may be noticed but the diagnosis isn't usually made until the age of three or later, when other features become apparent.

Genetic tests can confirm the diagnosis. These may be done antenatally using CVS or amniocentesis if there's known to be a risk. However, in most cases the condition does not recur within one family.

There's no cure for Angelman syndrome. Support for specific problems such as learning difficulties is important.

This article was last medically reviewed by Dr Rob Hicks in October 2007