Russell-Silver syndrome, also known as Silver-Russell syndrome, is a rare growth disorder estimated to affect between 1 in 15,000 children.

There are two main genetic abnormalities known to cause Russell-Silver syndrome, on either chromosome 7 or chromosome 11. These abnormalities have been found in up to 60% of SRS patients. In ~40% of SRS patients, the underlying cause is unknown.

Genes are made up of DNA. For most genes, both copies will be “turned on” and considered active. Genes are commonly “turned off” and considered inactive by a process called DNA methylation. For some genes, one copy is “turned off” and considered inactive and only one copy is “on” or active. The parent the copy is from dictates whether the gene is “on” or “off”. This is called genetic imprinting.

Genetic imprinting is important for normal development. You may hear Russell-Silver syndrome referred to as an imprinting disorder.

In around 30–60% of people with Russell-Silver syndrome, the cause is due to loss of methylation of a gene (i.e., “turns off” a gene) on chromosome 11 which causes the abnormality that may play a role in the development of SRS.

About 5–10% of people with Russell-Silver syndrome have mistakenly inherited two copies of chromosome 7 from their mother, rather than one from each parent. This is called maternal uniparental disomy.

Rarely, Russell-Silver syndrome can be caused by mutations in a series of genes on chromosome 11: CDKNIC, IGF2, PLAG1 and HMGA2. It is seen in cases of parents who have children with Russell-Silver syndrome.

The symptoms of Russell-Silver syndrome can vary widely between different people. Some symptoms include:

• Large head in relation to body size
• Prominent forehead
• Triangular face shape
• Dental overcrowding and overbite
• Downturned corners of the mouth
• Low-set ears that are rotated back
• Different length arms and/or legs (limb asymmetry)
• Curved little finger
• Short stature
• Excessive sweating
• Low muscle mass

While a doctor will base a diagnose Russell-Silver syndrome primarily on the presence of certain characteristics, it can be difficult due to the wide variety and severity of the symptoms of Russell-Silver syndrome and their similarity with other growth disorders. Therefore, it is thought that a lot of people living with Russell-Silver syndrome are misdiagnosed or remain undiagnosed.

If your doctor suspects your child has Russell-Silver syndrome they will likely perform genetic testing, which also tells you the subtype.