Silver–Russell syndrome

Silver–Russell dwarfism, also called Silver–Russell syndrome (SRS) or Russell–Silver syndrome (RSS) is a growth disorder occurring in approximately 1/50,000 to 1/100,000 births. In the United States it is usually referred to as Russell–Silver syndrome, and Silver–Russell syndrome elsewhere. It is one of 200 types of dwarfism and one of five types of primordial dwarfism and is one of the few forms that is considered treatable in some cases.

There is no statistical significance of the syndrome occurring preferentially in either males or females.

Etiology

Its exact cause is unknown, but present research points toward a genetic component, possibly following maternal genes.

It involves hypomethylation of H19 and IGF2.^[1] In 10% of the cases the syndrome is associated with maternal uniparental disomy (UPD) on chromosome 7.^[2] This is an imprinting error where the person receives two copies of chromosome 7 from the mother (maternally inherited) rather than one from each parent.

Like other imprinting disorders (e.g. Prader–Willi syndrome, Angelman syndrome, and Beckwith–Wiedemann syndrome), Silver–Russell syndrome may be associated with the use of assisted reproductive technologies such as in vitro fertilization.^[3]

The oldest known male with the condition in the United Kingdom is Carl Haworth, born 14 February 1969.

Diagnosis and symptoms

A somewhat triangular-shaped head and delicate facial features are typical characteristics of Russell-Silver Syndrome.

Although confirmation of a specific genetic marker is in a significant number of individuals, there are no tests to clearly determine if this is what a person has. As a 'syndrome' a diagnosis is typically given for children upon confirmation of the presence of several 'symptoms' listed below.^[4] Symptoms are Intrauterine Growth Restriction (IUGR) combined with some of the following:

• Often small for gestational age (SGA) at birth (birth weight less than 2.8 kg)
• Feeding problems: the baby is uninterested in feeding and takes only small amounts with difficulty
• Hypoglycemia
• Excessive sweating as a baby, especially at night, and a greyness or pallor of the skin. This may be a symptom of hypoglycemia
• Triangular shaped face with a small jaw and a pointed chin that tends to lessen slightly with age. The mouth tends to curve down
• A blue tinge to the whites of the eyes in younger children
• Head circumference may be of normal size and disproportionate to a small body size
• Wide and late-closing fontanelle
• Clinodactyly
• Body asymmetry: one side of the body grows more slowly than the other
• Continued poor growth with no "catch up" into the normal centile lines on growth chart
• Precocious puberty (occasionally)
• Low muscle tone
• Gastroesophageal reflux disease
• A striking lack of subcutaneous fat
• Late closing of the opening between the heart hemispheres
• Constipation (sometimes severe)

The average adult height for patients without growth hormone treatment is 4'11" for males and 4'7" for females.^[5]

Treatment

The caloric intake of children with RSS must be carefully controlled in order to provide the best opportunity for growth.^[4] If the child is unable to tolerate oral feeding, then enteral feeding may be used, such as the percutaneous endoscopic gastrostomy.

In children with limb-length differences or scoliosis, physiotherapy can alleviate the problems caused by these symptoms. In more severe cases, surgery to lengthen limbs may be required. To prevent aggravating posture difficulties children with leg length differences may require a raise in their shoe.

Growth hormone therapy is often prescribed as part of the treatment of RSS. The hormones are given by injection typically daily from the age of 2 years old through teenage years. It may be effective even when the patient does not have a growth hormone deficiency. Growth hormone therapy has been shown to increase the rate of growth in patients^[6] and consequently prompts 'catch up' growth. This may enable the child to begin their education at a normal height, improving their self-esteem and interaction with other children. The effect of growth hormone therapy on mature and final height is as yet uncertain.^[7] There are some theories suggesting that the therapy also assists with muscular development and managing hypoglycemia.

Eponym

It is named for Henry Silver and Alexander Russell.^[8][9][10]

References

External links

• Russell-Silver Support.Org
• GeneReviews/NCBI/NIH/UW entry on Russell-Silver Syndrome
• Russell-Silver Syndrome Support - www.rss-support.nl
• http://www.facebook.com/groups/rss.people/#!/groups/rss.people/ (TARSS, Group for teens and adults with Russell Silver Syndrome)
• "Russell Silver Syndrome (RSS)". Child Growth Foundation. 
• The MAGIC Foundation, RSS Division