Definition of Angelman syndrome
Angelman syndrome: An important genetic syndrome characterized by severe motor and intellectual retardation, microcephaly (abnormally small head), ataxia, frequent jerky limb movements and flapping of the arms and hands, hypotonia (floppiness), hyperactivity, seizures, absence of speech, frequent smiling and outbursts of laughter, and an unusual facies (facial appearance) characterized by macrostomia (large mouth), a large jaw and open-mouthed expression, and a great propensity for protruding the tongue (tongue thrusting). The name Angelman syndrome is now preferred because the old term "happy puppet syndrome" may appear derisive to the child's family.
Angelman syndrome is due in most cases to a chromosome deletion involving loss of material from chromosome region 15q11-q13. The loss is consistently of the contribution of chromosome region 15q11-q13 from the mother. This loss is due to a new deletion in most cases.
Deletion of chromosome region 15q11-q13 causes both Angelman syndrome and a totally different disorder called Prader-Willi syndrome. However, while the deleted chromosome is of maternal origin in Angelman syndrome, it is the paternal chromosome that is partially deleted in the Prader-Willi syndrome.
There are rare families with more than one child with Angelman syndrome. The mode of inheritance in these families is autosomal dominant modified by imprinting.
Last Editorial Review: 4/14/2001 7:06:00 PMCommon Misspellings: angelman syndrone
- Birth Defects - Read about birth defects, the leading cause of infant mortality during the first year. Causes of birth defects include ingestion of drugs or alcohol during pregnancy, genetic, hereditary, or environmental factors.
- Prader-Willi Syndrome - Read about Prader-Willi syndrome, a genetic condition characterized by weak muscle tone, feeding problems, delayed growth and development, which eventually leads to severe obesity. Prader-Willi syndrome is a defect in chromosome 15.
- Genetic Disease - Learn about genetic disease caused by abnormalities in an individual's genome. There are four types of genetic inheritance, single, multifactoral, chromosome abnormalities, and mitochondrial inheritance. Genetic testing is available for some genetic diseases.
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