Other Names for this Disease
- Silver-Russell dwarfism
- Silver-Russell syndrome
Your QuestionMy boyfriend has Russell-Silver syndrome. We are planing to have a baby. Will our baby inherit this condition from him?
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Under normal circumstances, each individual inherits one copy of each chromosome from their mother and one copy from their father. For most genes, both copies are expressed, or 'turned on,' in cells. For some genes, however, only the copy inherited from a person's father (the paternal copy) is expressed. For other genes, only the copy inherited from a person's mother (the maternal copy) is expressed. These parent-specific differences in gene expression are caused by a phenomenon called genomic imprinting. Both chromosome 7 and chromosome 11 contain groups of genes that normally undergo genomic imprinting. Abnormalities involving these genes appear to be responsible for many cases of Russell-Silver syndrome.
Researchers suspect that at least one third of all cases of Russell-Silver syndrome result from changes in a process called methylation, a chemical reaction that attaches small molecules called methyl groups to certain segments of DNA. In genes that undergo genomic imprinting, methylation is one way that a gene's parent of origin is marked during the formation of egg and sperm cells. Russell-Silver syndrome has been associated with changes in methylation involving the H19 and IGF2 genes, which are located near one another on chromosome 11. These genes are thought to be involved in directing normal growth. A loss of methylation disrupts the regulation of these genes, which leads to slow growth and the other characteristic features of this disorder.
Abnormalities involving genes on chromosome 7 may also cause Russell-Silver syndrome. In 7 percent to 10 percent of cases, people inherit both copies of chromosome 7 from their mother instead of one copy from each parent. This phenomenon, called maternal uniparental disomy (UPD), causes people to have two active copies of maternally expressed imprinted genes rather than one active copy from the mother and one inactive copy from the father. These individuals do not have a paternal copy of chromosome 7 and therefore do not have any copies of genes that are active only on the paternal copy. In cases of Russell-Silver syndrome caused by maternal UPD, an imbalance in active paternal and maternal genes on chromosome 7 underlies the signs and symptoms of the disorder.
In at least 40 percent of people with Russell-Silver syndrome, the cause of the condition is unknown. Researchers are working to identify additional genetic changes that underlie this disorder.
The following online resources can help you find a genetics professional in your community:
- The National Society of Genetic Counselors provides a searchable directory of US and international genetic counseling services.
- The American College of Medical Genetics has a searchable database of US genetics clinics.
- The University of Kansas Medical Center provides a list of US and international genetic centers, clinics, and departments.
- The American Society of Human Genetics maintains a database of its members, which includes individuals who live outside of the United States. Visit the link to obtain a list of the geneticists in your country, some of whom may be researchers that do not provide medical care.
- Russell-Silver syndrome. Genetic Home Reference. 2008; http://ghr.nlm.nih.gov/condition=russellsilversyndrome. Accessed 11/30/2011.
- Saal HM. Russell-Silver Syndrome: Genetic Counseling . GeneReviews. June 2, 2011; http://www.ncbi.nlm.nih.gov/books/NBK1324/#rss.Genetic_Counseling. Accessed 11/30/2011.