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Description and Causes
Smith-Magenis syndrome is a distinct and clinically recognizable contiguous gene syndrome characterized by a specific pattern of physical, behavioral, and developmental features. Smith-Magenis syndrome (SMS) is caused by a de novo genetic change early in embryonic development resulting in the interstitial deletion of the chromosome 17p11.2 region. The severity of the syndrome depends upon the amount of missing genetic material.
Affected individuals may have a variety of associated symptoms and physical abnormalities, including cranio-facial dysmorphias, brachycephalia, skeletal, ocular, cardiac, genitourinary and otolaryngological anomalies such as hearing loss and an unusually deep, hoarse voice. The central nervous system is affected, with observed psychomotor retardation and intellectual deficit. Behavioral troubles are frequent, including self-injurious behavior. Some people with SMS may never show significant behavior problems, although some degree of self-injury and sleep disturbance occurs in most. Self-injurious behavior is correlated with increasing age and a lower level of intellectual functioning.
Despite their very difficult behaviors, children and adults with SMS are very appealing and affectionate. Infants have a cherubic appearance and happy disposition. IQ is generally between 20 and 70, with most affected individuals falling in the moderate range of mental retardation (40 – 54).
The search for information on SMS is formidable since public and professional awareness about SMS and its implications is not widespread. No medical prevention or cure exists at this time.
Diagnosis can be made in the pre-natal period. Diagnosis is usually confirmed through karyotyping and fluorescence in situ hybridization for the interstitial 17p11.2 deletion during the evaluation of developmental delay and/or congenital anomalies. SMS is underdiagnosed. With improved molecular cytogenetic techniques and increased professional awareness of SMS, the number of SMS diagnoses grows every year. SMS babies often are thought to have Down Syndrome.
MEDICAL MANAGEMENT CONSIDERATIONS
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Note: These considerations are in addition to the normal medical care provided to an individual without Smith-Magenis syndrome. All recommendations can be addressed through clinical examination by the primary care provider, unless otherwise noted.
Infancy or Early Childhood (Birth to 5 years)
Late Childhood (5 to 13 years)
Adolescence and Adulthood (13 years and over)
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Peer-reviewed Journal Articles/Academies
Allanson, J.E., Greenberg, F., Smith, A.C. (1999). The Face of Smith-Magenis Syndrome: A Subjective and Objective Study. Journal of Medical Genetics, 36(5), 394-397.
Dykens, E.M., Smith, A.C. (1998). Distinctiveness and Correlates of Maladaptive Behaviour in Children and Adolescents with Smith-Magenis Syndrome. Journal of Intellectual Disability Research, 42(6), 481-489.
Finucane, B.M., Haines-Dirrigl, K., Simon, E. (2001). Characterization of Self-injurious Behaviors in Children and Adults with Smith-Magenis Syndrome. American Journal on Mental Retardation, 106(1), 52-59.
Finucane, B.M. et al. (1993). Eye Abnormalities in the Smith-Magenis Contiguous Gene Deletion Syndrome. American Journal of Medical Genetics, 45(4), 443-446.
Finucane, B.M. et al. (1994). The Spasmodic Upper-body Squeeze: A Characteristic Behavior in Smith-Magenis Syndrome. Developmental Medicine and Child Neurology, 36(1), 78-83.
Greenberg, F. et al. (1991). Molecular Analysis of the Smith-Magenis Syndrome: A Possible Contiguous-gene Syndrome Associated with Del(17), (p.11.2). American Journal of Human Genetics, 49(6), 1207-1218.
Greenberg, F. et al. (1996). Multi-disciplinary Clinical Study of Smith-Magenis Syndrome (deletion 17p11.2). American Journal of Medical Genetics, 62(3), 247-254.
Hodapp, R.M., Fidler, D.J., Smith, A.C. (1998). Stress and Coping in Families of Children with Smith-Magenis Syndrome. Journal of Intellectual Disability Research, 42(5),331-340.
Smith, A. C., Dykens, E., Greenberg, F. (1998). Behavioral phenotype of Smith-Magenis Syndrome (del17 p11.2). American Journal of Medical Genetics, 81(2), 179-185.
Smith, A.C., Dykens, E., Greenberg, F. (1998). Sleep Disturbance in Smith-Magenis Syndrome (del17 p11.2). American Journal of Medical Genetics, 81(2), 186-191.
Smith, A.C., Gropman, A. (2001). Smith-Magenis Syndrome. In S.B. Cassidy, J.E. Allanson (Eds.) Management of Genetic Syndromes (pp. 363-385). New York: Wiley-Liss.
Sweeney, E. et al. (1999). Smith Magenis Syndrome and Tetralogy of Fallot. American Journal of Medical Genetics, 36(6), 501-502.
Thoene, J.G., (ed.) (1995). Physicians’ Guide to Rare Diseases, 2nd Ed. Montvale, NJ: Dowden.
Special Interest Groups/Other Publications
4301 Connecticut Avenue NW, #404
Washington, DC 20008-2304
(800) 336-GENE helpline
(202) 966-8553 fax
National Organization for Rare Disorders, Inc. (NORD)
PO Box 8923
New Fairfield, CT 06812-8923
RESOURCES FOR FAMILIES
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Parents & Researchers Interested in Smith-Magenis Syndrome (PRISMS)
76 South New Boston
Francestown, NH 03043
Smith-Magenis Syndrome Contact Group
52 Ladeside Close
Glasgow, Scotland G77-6TZ United Kingdom
Smith-Magenis Syndrome Mailing List
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Theodore A. Kastner, M.D., M.S.
Robin L. Hansen, M.D.
Patrick J. Maher, M.D.
Terrance D. Wardinsky, M.D.
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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.