Description and Cause
Angelman Syndrome is a genetic disorder characterized by physical abnormalities and impairments in neurological, motor, and intellectual functioning. It may be caused by (1) maternal deletion on the long arm of chromosome 15 in up to 80% of cases; (2) uniparental disomy (both chromosomes 15 of paternal origin) in 3-4% of cases; (3) an imprinting defect or genetic mutation in 5% of cases; or (4) an unknown cause in 10-15% of cases. (Note: Prader-Willi Syndrome is often discussed with Angelman Syndrome because they share a similar genetic basis; return to the index to view a document on Prader-Willi Syndrome.)
Note: These considerations are in addition to the normal medical care provided to an individual without Angelman Syndrome. All recommendations can be addressed through clinical examination by the primary care provider, unless otherwise noted.
Because persons with Angelman Syndrome often exhibit profound communication deficits, inattentiveness and hyperactivity, many clinicians, educators and caregivers assume that profound functional impairment is inevitable. However, affected individuals may overcome many challenges and achieve developmental progress if appropriate interventions are delivered. It is important to emphasize nonverbal skills in measuring cognitive capabilities; although speech is absent or extremely limited, most individuals are able to understand verbal language very well. Many individuals with Angelman Syndrome are able to participate in group activities, perform household chores, and provide self-care. Typically, the primary care physician’s main focus is on seizure management.
Note: Diagnosis is usually not made until after 12 months of age, and may not be made until late childhood or adulthood. In any case, the following should be performed as soon as diagnosis is suspected.
Ongoing (all ages)
Childhood (1 to 13 years)
Adolescence and Adulthood (13 years and over)
Peer-reviewed Journal Articles/Academies
Buckley, R.H. et al. (1998). Angelman Syndrome: Are the Estimates Too Low? American Journal of Medical Genetics, 80(4), 385-390.
Cassidy, S.B., Schwartz, S. (1998). Prader-Willi and Angelman Syndromes: Disorders of Genomic Imprinting. Medicine, 77(2), 140-151.
Malcolm, S, et al. (1991). Uniparental Paternal Disomy in Angelman’s Syndrome. Lancet, 337(8743), 694-697.
Penner, K.A. et al. (1993). Communication, Cognition, and Social Integration in the Angelman Syndrome. American Journal of Medical Genetics, 46, 34-39.
Summers, J.A. et al. (1995). Behaviour Problems in Angelman Syndrome. Journal of Intellectual Disability Research, 39(2), 97-106.
Special Interest Groups/Other Publications
Angelman Syndrome Foundation (USA). Facts About Angelman Syndrome. Accessed March 29, 1999
Capute, A.J., Accardo, P.J. (1996). Developmental Disabilities in Infancy and Childhood vol. I: Neurodevelopmental Diagnosis and Treatment. Baltimore: Paul H. Brookes.
Capute, Arnold J. and Pasquale J. Accardo. (1996). Developmental Disabilities in Infancy and Childhood vol II: The Spectrum of Developmental Disabilities. Baltimore: Paul H. Brookes.
Miller, L. (1995). (revised 1999). Angelman Syndrome: A Parent’s Guide. (Master’s thesis). Accessed March 29, 1999 at members.aol.com/miller566/as_paper.htm. [Note: site no longer exists] Spanish version available
Angelman Syndrome Foundation
California Department of Developmental Services
California Regional Centers
Canadian Angelman Syndrome Society
Exceptional Parent Magazine
March of Dimes Birth Defects Foundation
Theodore A. Kastner, M.D., M.S.
Felice Weber Parisi, M.D., M.P.H.
Romie H. Holland, M.D.
Patricia Samuelson, M.D.
This document does not provide advice regarding medical diagnosis or treatment for any individual case, and any opinions or statements contained in this document are not intended to serve as a standard of medical care. Physicians are encouraged to view the considerations presented in this document in light of evolving scientific information. This document is not intended for use by the layperson. Reproduction of this document may be done with proper credit given to California Department of Developmental Services.
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