Russell-Silver syndrome

Definition

Russell-Silver syndrome is a disorder present at birth and diagnosed no later than early childhood. It is characterized by poor growth demonstrated by low birth weight and short stature (adult height usually less than 5 feet) and, frequently, asymmetry in the size of the two halves or other parts of the body.

The facial features may have a characteristic appearance:

• triangular shape with broad forehead
• small pointed chin
• thin wide mouth

Children with Russell-Silver syndrome are at risk for developmental and motor delays as well as learning disabilities.

Causes, incidence, and risk factors

There is no one cause known for this rare disorder. Most cases are sporadic, that is, occur as an isolated finding in a family with no other affected family member.

The features associated with Russell-Silver syndrome have been described in association with many genetic abnormalities such as:

• chromosome rearrangements
• uniparental disomy (UPD) 7
• autosomal dominant and recessive families (rarely reported)

More than 400 cases have been reported. Estimates of incidence range from as high as 1 in 3,000 to as low as 1 in 100,000. Males and females are equally affected.

Symptoms

• low birth weight
• poor growth during infancy and childhood
• proportionally short stature with normal skeleton and frequently delayed bone age
• normal head circumfrence, often with the appearance of "pseudohydrocephalus"
• typical facial characteristics include a broad, prominent forehead with small triangular face and small, narrow chin
• limbs of differing lengths
• fifth finger clinodactyly (curving of the pinky toward the ring finger)
• brachydactyly (short, stubby fingers and toes)
• cafe-au-lait (coffee with milk) colored spots
• arm span less than height (short arms)

Signs and tests

The following genitourinary problems may be present:

• Hypospadias (abnormality where the urethra exits the body underneath the penis, rather than at the tip) and cryptorchidism (undescended testes)
• Kidney anomalies, such as:
  • hydronephrosis
  • renal tubular acidosis
  • posterior urethral valves
  • horseshoe kidney

The following gastrointestinal disorders may be present:

• Gasroesophageal reflux disease
• Esophagitis
• Food aversion
• Failure to thrive

There are no specific laboratory tests for the diagnosis of Russell-Silver syndrome.

Tests may be performed as follows:

• Blood sugar
• Growth hormone
• Skeletal survey, to exclude skeletal dysplasia, which may mimic Russell-Silver syndrome
• tests to determine chromosome abnormalities
• test to determine if bone age is delayed

It is estimated that 7-10% of patients with RSS have a defective gene (maternal uniparental disomy for chromosome 7). The great majority of patients with RSS to date have no identifiable cause for their diagnosis.

Treatment

The predominant treatment goals pertain to stature and growth.

• growth hormone replacement may be helpful if a growth hormone deficiency is discovered
• optimal calorie intake
• early intervention
• physical therapy
• special education

Expectations (prognosis)

Older children and adults do not show typical features as clearly as infants or younger children. Intelligence may be normal, although the patient may have a learning disability.

Complications

• self esteem and emotional problems related to appearance
• chewing or speaking difficulty if jaw is very small
• learning disablities

Calling your health care provider

Many specialists may be involved in treatment depending upon the physical features and developmental concerns.

• Clinical geneticist to help with the diagnosis of Russell-Silver syndrome.
• Gastroenterologist or nutritionist to optimize caloric intake and enhance growth and feeding therapy.
• Developmental evaluation places the patient in early intervention, special education programs, physical therapy and occupational therapy as early as possible.
• Endocrinologist to consider the use of a growth hormone when the child is school-aged.

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