What are the genetic changes related to Smith-Magenis syndrome ?
Most people with Smith-Magenis syndrome have a deletion of genetic material from a specific region of chromosome 17. Although this region contains multiple genes, researchers believe that the loss of one particular gene, RAI1, in each cell is responsible for most of the characteristic features of this condition. The loss of other genes in the deleted region may help explain why the features of Smith-Magenis syndrome vary among affected individuals.  A small percentage of people with Smith-Magenis syndrome have a mutation in the RAI1 gene instead of a chromosomal deletion. Although these individuals have many of the major features of the condition, they are less likely than people with a chromosomal deletion to have short stature, hearing loss, and heart or kidney abnormalities.  The RAI1 gene provides instructions for making a protein whose function is unknown. Mutations in one copy of this gene lead to the production of a nonfunctional version of the RAI1 protein or reduce the amount of this protein that is produced in cells. Researchers are uncertain how changes in this protein result in the physical, mental, and behavioral problems associated with Smith-Magenis syndrome.