What are the other Names for this Condition? (Also known as/Synonyms)

• Edwards Syndrome
• T18 Syndrome
• Trisomy E

What is Trisomy 18 Syndrome? (Definition/Background Information)

• Trisomy 18 Syndrome is a genetic disorder characterized by the presence of an extra 18th chromosome material. The abnormal cells may have entire extra chromosome 18 or may have extra partial 18 chromosomes. Based on this, the syndrome could either be a Complete Trisomy 18 or a Partial Trisomy 18
• Typically, a single pair (or 2 numbers) of chromosome 18 is present; but, in this condition an extra chromosome 18 is observed, making it 3 (hence the term Trisomy 18). This syndrome affects normal growth and development, due to the presence of the extra genetic material
• Trisomy 18 Syndrome is also referred to as Edwards Syndrome and is the most common autosomal syndrome, after Down syndrome
• The mortality rate is very high in children with this disorder; most deaths occurring before the child is born
• There is no cure for the condition and the treatment measures followed are mostly symptomatic. The prognosis for Trisomy 18 Syndrome is poor

Who gets Trisomy 18 Syndrome? (Age and Sex Distribution)

• The incidence rate for Trisomy 18, in both sexes (taken together) is 1 in 6000 live births
• Females are affected about 3-4 times more than males
• No particular racial or ethnic predilection is observed

What are the Risk Factors for Trisomy 18 Syndrome? (Predisposing Factors)

Trisomy 18 Syndrome risk factors include:

• There seems to be link between the maternal age (during pregnancy) and the onset of this disorder, with an increasing maternal age, increasing the risk
• Female babies are at a much higher risk than male babies

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases ones chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Trisomy 18 Syndrome? (Etiology)

• Trisomy 18 Syndrome takes place due to a chromosomal anomaly, when an additional copy of the genetic material found on the 18th chromosome is carried forward during fertilization. If all of the genetic material is copied and taken forward, then it is termed as a Complete Trisomy 18, else it is termed Partial Trisomy 18
• The extra material causes 47 chromosomes (23 pairs and a single extra 18th chromosome) to be present in the developing fetus, leading to serious medical complications. Under normal circumstances, a healthy egg and sperm contributes 23 (haploid) chromosomes each, totaling 46 chromosomes to the developing fetus.
• It is researched that the cause may lie either in the egg cell or in the sperm cell (maybe a cell division error), which after fertilization creates three copies (trisomy) of the 18th chromosome, rather than 2 normal copies
• In some cases, all body cells are not found to have this extra chromosome, but only a small proportion of cells are found to have them. This causes a mixed cell population with different chromosome numbers (quantity) known as ‘Mosaic Edwards Syndrome’. In such cases, the severity of the signs and symptoms are less than those observed with a CompleteT18 Syndrome. Despite this, a Partial Mosaic Edwards Syndrome could still be fatal
• A Trisomy 18 Syndrome occurs at the genetic level; it is currently researched that all cases of T18 Syndrome occur spontaneously, by chance

What are the Signs and Symptoms of Trisomy 18 Syndrome?

Most pregnancies are terminated and most babies die, before or immediately following birth; Trisomy 18 Syndrome has a high fatality rate. However, of the surviving few, the signs and symptoms are mainly related to growth deficiencies and delayed or imbalanced development. All the vital organs, such as the brain, heart, and kidneys, can be affected.

• In newborn babies, the following signs and symptoms of T18 Syndrome are generally observed:
  • Clenched fists
  • Clubfoot
  • Mental deficiencies
  • Small head and jaw
  • Odd-shaped chest
  • Low birth weight
  • Cleft lip and palate
• A developing fetus in the womb may show:
  • Heart and nervous system abnormalities
  • Fluid in the brain

How is Trisomy 18 Syndrome Diagnosed?

Diagnosis for Trisomy 18 Syndrome, may be made through physical examination of the infant after birth, or while the fetus is in the womb. These can be confirmed through karyotyping (analysis of chromosomes), by taking a sample of the blood or amniotic fluid.

• Some of the physical signs of Trisomy 18, noted in a pregnant woman are: A large uterus, larger quantity of amniotic fluid, and a very small placenta
• The new born infant may show strange fingerprint patterns, breastbone defects (which can be seen in an x-ray), abdominal muscle defects, congenital eye (iris), heart and kidney related defects

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Trisomy 18 Syndrome?

Complications that develop due to Trisomy 18 Syndrome, depends on the severity of the syndrome. Partial Trisomy 18 has less severe signs and syndrome compared to complete Trisomy 18.

• Complications also depend on the kind of specific defects and abnormalities that are observed
• Due to very low survival rates, most children do not make it beyond the age of 10 years; also, only partial Trisomy 18 affected children, survive this long. Complete Trisomy 18 affected newborn children, survive for a very short time period

How is Trisomy 18 Syndrome Treated?

An individualized treatment (a case-by-case approach) is planned and provided for Trisomy 18 Syndrome, based on the specific conditions/complications that develop.

• Both partial T18 Syndrome and complete T18 Syndrome have no known cures
• The treatment provided is often symptomatic

How can Trisomy 18 Syndrome be Prevented?

• Currently, there are no specific methods or guidelines to prevent Trisomy 18 Syndrome genetic condition
• Genetic testing of the expecting parents (and related family members) and prenatal diagnosis (molecular testing of the fetus during pregnancy) may help in understanding the risks better during pregnancy
• If there is a family history of the condition, then genetic counseling will help assess risks, before planning for a child
• Active research is currently being performed to explore the possibilities for treatment and prevention of inherited and acquired genetic disorders

What is the Prognosis of Trisomy 18 Syndrome? (Outcomes/Resolutions)

• Trisomy 18 Syndrome (Partial or Complete) is a fatal genetic disorder. Most children, who survive the disorder (barely to the early teens), are severely affected by birth defects and developmental deformities
• Medical researchers are still trying to understand Trisomy 18 Syndrome and find a way to prevent its occurrence

Additional and Relevant Useful Information for Trisomy 18 Syndrome:

There are voluntary organizations and support groups that provide help and understanding to the families and parents of the Trisomy affected.