This information is provided by the National Institutes of Health (NIH) Genetic and Rare Diseases Information Center (GARD).
Smith-Magenis syndrome (SMS) is a developmental disorder that affects many parts of the body. The major features of this condition include mild to moderate intellectual disability, delayed speech and language skills, distinctive facial features, sleep disturbances, and behavioral problems. Most people with SMS have a deletion of genetic material in each cell from a specific region of chromosome 17. Although this region contains multiple genes, researchers believe that the loss of one particular gene, RAI1, is responsible for most of the features of the condition. In most of these cases, the deletion is not inherited, occurring randomly during the formation of eggs or sperm, or in early fetal development. In rare cases, the deletion is due to a chromosomal balanced translocation in one of the parents. In about 10% of cases, SMS is caused by a mutation in the RAI1 gene. These mutations may occur randomly, or may be inherited from a parent in an autosomal dominant manner. Treatment for SMS depends on the symptoms present in each person.
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