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What is Angelman syndrome?
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What is Angelman syndrome?

Angelman syndrome (AS) is a genetic disorder which causes severe developmental delay. The most striking symptoms are mental retardation, a severe speech disorder (in most cases, lack of speech), gross and fine motor difficulties, a short attention span as well as some behaviorally unique features such as hand flapping, hypermotoric behavior, an easily excitable personality and a frequently happy demeanor. In addition, some individuals with AS exhibit a suck/swallowing disorder and/or frequent tongue thrusting, sometimes accompanied by drooling. Other common features include wide-spaced teeth and hypopigmentation (lighter skin and hair than their family members). (also see Consensus Criteria below and search our database of subjects, who include a wide range of ages, backgrounds, ethnicities, and genetic diagnoses)

Some of the most difficult issues faced by families and caregivers include the common onset of seizures during childhood, a difficult sleep pattern (individuals with AS often seem to need hardly any sleep at all), and communication. Communication is an especially complex issue, because even though most AS individuals don't have any speech at all, they understand a lot of what is said to them. In order for them to be able to express themselves, alternative methods of communication have to be established, which can be a long and difficult process. The issue of communication is explored in depth as part of The Angelman Project. Other important topics explored in The Angelman Project include schooling, housing and job/activity provision for adults, behavioral issues and physical therapies, among others. (Search our database for in-depth information and CD collections on all these issues)

Angelman syndrome is caused by a missing or "faulty" genetic code on chromosome #15. To date, there are four distinct known genetic causes for AS that can be determined by genetic testing. These four separate diagnoses, which all cause the same syndrome, but with some variations in the symptoms, are as follows: deletion+, uniparental disomy (UPD), imprinting and UBE3A, which is the only hereditary diagnosis. For more detail, please see the Genetics section below or refer to films featuring Dr. Jill Clayton-Smith and Dr. Charles Williams.

Diagnosis/testing "Consensus clinical diagnostic criteria for AS have been developed, but the mainstay of diagnosis testing is: 1) analysis of parent-specific DNA methylation imprints in the 15q11-q13 chromosome region, which detects ~78% of patients with AS, including those with a deletion, uniparental disomy, or imprinting defect; and 2) mutation analysis of the UBE3A gene, which detects an additional ~11% of patients. Less than 1% of patients have a cytogenetically visible chromosome rearrangement. The remaining ~11% patients with classic phenotypic features of AS have a presently unidentified genetic mechanism and thus are not amenable to diagnostic testing."

Genetic counseling "AS is caused by the loss of maternally imprinted contribution(s) in the 15q11-q13 (AS/PWS) region that can occur by at least five different known genetic mechanisms. The risk to sibs of an affected child of having AS depends upon the genetic mechanism of the loss of the maternally contributed AS/PWS region. The risk to sibs of an affected child who has a deletion or uniparental disomy is typically <1%. The risk is as high as 50% to the sibs of a child with an imprinting defect or a mutation of the UBE3A gene. Members of the mother's extended family are also at increased risk when an imprinting defect or a UBE3A mutation is present. Cytogenetically visible chromosome rearrangements may be inherited or de novo. Prenatal testing is possible when the underlying genetic mechanism is deletion, uniparental disomy, imprinting defect, UBE3A mutation, or chrosmosome

*"Angelman Syndrome" Authors: Charles A Williams, MD; Amy C Lossie ; Daniel J Driscoll, PhD, MD Initial Posting: 15 September 1998 Last Update: 21 November 2000 In: GeneReviews at GeneTests·GeneClinics: Medical Genetics Information Resource (database online). Copyright, University of Washington, Seattle. 1997-2002. Accessed 8.21.02.
Available at www.GeneClinics.Org or www.GeneTests.Org

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Click Here to Read Our Chapter:
Genetic counseling for Angelman syndrome (AS) by Jill E. Hendrickson, MS, MSSW (CGC)

An example of hypopigmentation in an individual with a Deletion + diagnosis of AS -- our subject of the month, Lavania, has lighter skin color than the other members of her family.

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