NORD gratefully acknowledges Ann C.M. Smith, M.A., D.Sc.(Hon), Sr. Genetic Counselor/Contractor, SMS Research Studies, Office of the Clinical Director, National Human Genome Research Institute, National Institutes of Health, for assistance in the preparation of this report.
Smith-Magenis syndrome (SMS) is a complex developmental disorder that affects multiple organ systems of the body. The disorder is characterized by a pattern of abnormalities that are present at birth (congenital) as well as behavioral and cognitive problems. Common symptoms include distinctive facial features, skeletal malformations, varying degrees of intellectual disability, speech and motor delays, sleep disturbances, and self-injurious or attention-seeking behaviors. The specific symptoms present in each case can vary dramatically from one individual to another. Approximately 90% of cases are caused when a portion of chromosome is missing or deleted (monosomic). This deleted portion within chromosome 17p11.2 includes the RAI1 gene, which is believed to play a major role in the development of the disorder. Other genes within the deleted segment may also play a role in variable features in the syndrome, but it is not fully understood how significant a role they play in the development of SMS. In the remaining cases, there is no deleted material on chromosome 17; these cases are caused by mutations in the RAI1 gene.
Smith-Magenis syndrome was first reported in the medical literature in 1982 by Ann Smith, a genetic counselor, and colleagues. In 1986, Smith and Dr. R. Ellen Magenis identified nine patients with the disorder further delineating the syndrome. Since that time numerous additional cases have been identified allowing physicians/clinicians to develop a better understanding about this complex disorder.
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