Russell-Silver Syndrome Health Article

Definition

Russell-Silver syndrome (RSS) is one of the recognized forms of intrauterine growth retardation (IUGR) diseases. It was first independently described by H. K. Silver in 1953 and by A. Russell in 1954.

Description

Russell-Silver syndrome is one of more than 300 recognized forms of genetic disorders that lead to short stature. It is characterized by:

• the presence of a triangular shaped face
• an incurving fifth finger (clinodactyly)
• low birth weight and length (intrauterine growth retardation, or IUGR)
• a poor appetite in the first few years of life

This disorder is alternately known as Russell syndrome, Silver syndrome, or Silver-Russell syndrome. Some clinicians use the term Russell syndrome to indicate this disorder when the size of the sides of the body and the limbs are equal, and the term Silver syndrome to indicate this disorder when the size of the sides of the body or the length of the limbs is different (body asymmetry).

Genetic profile

The exact genetic cause, or causes, of RSS have not been fully identified. It is currently believed that almost all cases of RSS are the result of mutations on a gene, or possibly more than one gene, on chromosome 7.

Demographics

RSS occurs in approximately one in every 200,000 live births. Almost all cases of RSS are sporadic, that is, they appear for the first time in individuals with no family history of RSS. However, case studies indicating all three modes of inheritance—autosomal recessive, autosomal dominant, and X-linked—have been reported.

RSS does not appear to affect any particular race or ethnic group in a greater frequency than others. It is also observed equally in males and females.

Signs and symptoms

There are six characteristics that define Russell-Silver syndrome: a triangular shaped face; down turned corners of the mouth; inwardly curved little fingers (clinodactyly); a combination of low birth weight (intrauterine growth retardation) and short birth length after a full term gestation; a long, narrow head (scaphocephaly); and a poor appetite that causes slow growth after birth. These characteristics are commonly observed in people affected with RSS.

Several other characteristics are found in most, but not all, RSS affected individuals. These include:

• low blood sugar (hypoglycemia) in infancy and early childhood
• unequal body and limb size from one side of the body to the other (body asymmetry)
• late closure of the soft spot in the front of the skull
• a broad forehead
• a small chin and jaw
• crowding of the teeth or abnormally small teeth caused by a smaller than normal jaw
• an abnormally thin upper lip
• low-set, small, and prominent ears
• fusion or webbing of the toes (syndactyly)
• poor muscle tone (hypotonia)
• a condition in which the bones are not as mature as the bones of a typical person of the same age (delayed bone age)
• developmental delays

In males affected with RSS, undescended testicles and a misplacement of the urethral opening (hypospadias) on the bottom of the penis rather than on the tip of the glans is often seen.

People affected with RSS may show other symptoms on a less uniform basis. These include:

• water on the brain
• a bluish coloration of the whites of the eyes
• a highly-arched palate
• an absence of certain teeth
• frequent ear infections caused by fluid in the ear, which can lead to temporary hearing loss
• migraine headaches
• a curvature of the spine (scoliosis) or other problems with the spine, often caused by body asymmetry
• abnormalities of the kidneys
• an abnormally early onset of puberty (precocious puberty)
• irregularly colored spots on the skin (café-au-lait spots)
• high energy levels
• attention deficit disorder (ADD)
• fainting spells

Diagnosis

Diagnosis of RSS is generally accomplished by performing a genetic test on cells grown from a skin sample. This test must be performed prior to the fifth year of life and it is not always accurate.

A diagnosis of RSS is supported by examination of the affected individual's growth curve and daily food intakes. In a child affected with RSS, these will fall well short of the mean for children of the same age.

Body measurements for asymmetry and x rays to determine the bone age versus the actual age of the patient are also useful. Additionally, a blood test indicating hypoglycemia may indicate RSS. When RSS is suspected in males, an examination of the genitals may reveal undescended testicles or a misplacement of the urethral opening.