Angelman Syndrome

Angelman syndrome (AS) is a genetic disorder that mainly affects the nervous system. Symptoms include a small head and a specific facial appearance, severe intellectual disability, developmental disability, speaking problems, balance and movement problems, seizures, and sleep problems. Children usually have a happy personality and have a particular interest in water. The symptoms generally become noticeable by one year of age.

AS affects 1 in 12,000 to 20,000 people. Males and females are affected with equal frequency. It is named after a British paediatrician, Harry Angelman, who first described the syndrome in 1965. An older term, "happy puppet syndrome", is generally considered pejorative. Prader–Willi syndrome is a separate condition, caused by a similar loss of the father's chromosome 15.

Some of the symptoms include:

1. Developmental delay, functionally severe
2. Speech impairment, no or minimal use of words; receptive and non-verbal communication skills higher than verbal ones
3. Movement or balance disorder, usual ataxia of gait and tremulous movement of limbsBehavioural uniqueness: any combination of frequent laughter/smiling; happy demeanour; easily excitable personality, often with hand flapping motions; hypermotoric behaviour; short attention span.

Angelman syndrome is caused by the loss of the average maternal contribution to a region of chromosome 15, most commonly by deletion of a segment of that chromosome. Other causes include uniparental disomy, translocation, or single gene mutation in that region. A healthy person receives two copies of chromosome 15, one from the mother, the other from the father. However, in the part of the chromosome that is critical for Angelman syndrome, the maternal and paternal contribution express specific genes very differently. This is due to sex-specific epigenetic imprinting; the biochemical mechanism is DNA methylation.