Russell-Silver syndrome


Russell-Silver syndrome

Description, Causes and Risk Factors:

Russell-Silver syndrome is a growth disorder characterized by slow growth before and after birth. Babies with this condition have a low birth weight and often fail to grow and gain weight at the expected rate (failure to thrive). Head growth is normal, however, so the head may appear unusually large compared to the rest of the body. Affected children are thin and have poor appetites, and some develop low blood sugar (hypoglycemia) as a result of feeding difficulties. Adults with Russell-silver syndrome are short; the average height for affected males is about 151 centimeters (4 feet, 11 inches) and the average height for affected females is about 140 centimeters (4 feet, 7 inches).

Many children with Russell-Silver syndrome have a small, triangular face with distinctive facial features including a prominent forehead, a narrow chin, a small jaw, and down-turned corners of the mouth. Other features of this disorder can include an unusual curving of the fifth finger (clinodactyly), asymmetric or uneven growth of some parts of the body, and digestive system abnormalities. Russell-Silver syndrome is also associated with an increased risk of delayed development and learning disabilities.

The exact incidence of Russell-Silver syndrome is unknown, but the condition is estimated to affect 1 in 75,000 to 100,000 people.

The genetic causes of Russell-Silver syndrome are complex. The disorder often results from the abnormal regulation of certain genes that control growth. Research has focused on genes located in particular regions of chromosome 7 and chromosome 11.

People normally inherit 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. Methylation is 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.

Symptoms:

Symptoms that may occur with RSS include:

    Birthmarks that are the color of coffee with milk (cafe-au-lait marks).

  • Curving of the pinky toward the ring finger.

  • Delayed bone age.

  • Failure to thrive.

  • Gastroesophageal reflux disease (GERD).

  • Kidney problems, such as:

  • Horseshoe kidney.

  • Hydronephrosis.

  • Posterior urethral valves.

  • Renal tubular acidosis.

  • Low birth weight.

  • Large head for body size.

  • Poor growth.

  • Short arms.

  • Short height (stature).

  • Short, stubby fingers and toes.

  • Delayed stomach emptying, and constipation.

  • Wide forehead with a small triangle-shaped face and small, narrow chin.

Diagnosis:

The condition is usually diagnosed by early childhood. The doctor will perform a physical exam. Signs include:

    Pointed chin that is not fully developed.

  • Thin, wide mouth.

  • Triangle-shaped face with broad forehead.

There are no specific laboratory tests to diagnose Russell-Silver syndrome. Diagnosis is usually based on the judgment of your child's Pediatrician. However, the following tests may be done:

    Blood sugar (some children may have low blood glucose).

  • Bone age testing (bone age is often younger than the child's actual age).

  • Chromosome testing (may detect a chromosomal problem).

  • Growth hormone (some children may have a deficiency).

  • Skeletal survey (to rule out other conditions that may mimic Russell-Silver syndrome).

Treatment:

Many specialists may be involved in treating this condition:

    A doctor specializing in genetics can help diagnose Russell-Silver syndrome.

  • A gastroenterologist or nutritionist can help develop the proper diet to enhance growth.

  • An endocrinologist may prescribe growth hormone, if it is needed.

  • Genetic counselors and psychologists may also be involved.

Treatment of RSS varies on a case-by-case basis depending on the symptoms of the affected individual.

Dietary changes to increase food intake are required by all people with RSS. Many patients with RSS also require a diet high in sugars to treat hypoglycemia. When the necessary food intake can not be accomplished by dietary changes, it may be necessary to treat patients with the antihistamine Periactin, which also serves as an appetite stimulant. Some patients may also benefit from a feeding pump or gastrostomy. Gastrostomy is a surgical procedure in which a permanent opening is made directly in the stomach for the introduction of food.

In cases of severe growth retardation, certain people will require the administration of an artificial form of growth hormone (recombinant growth hormone) to stimulate growth, increase the rate of growth, and to increase their final adult height.

Ear tubes may be required to improve fluid drainage from the ears of some patients affected with RSS.

In cases of body asymmetry, limb lengthening surgeries may be recommended. Alternatively, shoe lifts may be all that is necessary for the attainment of a normal gait.

Depending on the severity of physical, emotional, and psychological symptoms, some affected individuals may benefit from physical and/or occupational therapy. If ADD or other developmental problems exist, individuals with RSS may require educational assistance, such as remedial reading. In cases where the jaw is extremely small, talking may be difficult. These patients may require speech therapy.

Precocious puberty is the entrance of a child into puberty prior to the age of eight or nine. This early onset of puberty is generally accompanied by a growth spurt prior to puberty. While entering puberty before one is emotionally ready is certainly a serious problem, it is the growth spurt prior to puberty that is of major medical significance and concern.

If this growth spurt occurs prior to puberty, it is generally not as robust as if it had occurred during puberty, which causes the individual undergoing this growth spurt to grow less than a person who undergoes this process during puberty. The result is that a person who undergoes precocious puberty will generally end up much shorter in adulthood than his or her peers.

There are three hormonal therapies available in the United States to treat precocious puberty. Histrelin (trade name: Supprelin) is administered by daily injection. Leuprolide acetate (trade name: Lupron) is available as a depot formulation every four weeks. A depot formulation places medication in a tiny pump that is attached to the patient's body and releases the medication over time. Nafarelin acetate (trade name: Synarel) is administered as a nasal spray three times daily. Because of the age of people being treated, Lupron is most often the medication of choice because it is only administered once a month.

Some doctors have noticed that persons affected with RSS may have a slightly elevated chance of developing Wilm's tumor, the most common form of kidney cancer. Most cases of this type of cancer occur before the age of eight, and this condition is extremely rare in adults. It is important that children with RSS be screened with ultrasound every three months until the age of eight to make sure they have not developed Wilm's tumor. Wilm's tumor is quite treatable via surgery, chemotherapy, and/or radiation.

NOTE: The above information is for processing purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.

DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.

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