Edwards syndrome, also known as trisomy 18, describes a rare genetic condition where a person has three copies of chromosome 18. Having an extra copy of this chromosome causes a variety of symptoms that can result in severe complications.

Deoxyribonucleic acid, or DNA, is the molecule that carries genetic information for the development, growth, and reproduction of life. A person usually inherits one set of 23 chromosomes from one parent and another 23 from the other, totalling 46 chromosomes.

However, in some cases, a chromosomal aberration may occur. This term refers to alterations in the shape or number of chromosomes, which can impact development. With Edwards syndrome, a person has an extra copy of chromosome 18, which can lead to significant clinical consequences.

This article discusses Edwards syndrome, including its definition, causes, and symptoms.

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Trisomy 18, also known as Edwards syndrome, refers to a genetic condition that occurs due to having an extra chromosome 18 in some or all of the body’s cells. The name Edwards syndrome derives from Dr. John H Edwards, while trisomy 18 is in reference to the three copies of the chromosome.

Possessing an extra copy of this chromosome may impact the development of a fetus and cause the characteristic features of the condition. Many infants with Edwards syndrome may die before birth or early childhood, but some children live for several years.

Evidence suggests that the condition occurs in roughly 1 in 5,000 live-born infants. The incidence is higher during pregnancy, but many fetuses do not survive to term. While a person of any age can have a child with Edwards syndrome, the chances increase with age.

Unlike many other genetic conditions, a person does not typically inherit the genes for Edwards syndrome. Instead, an error in cell division known as nondisjunction occurs, which results in an egg or sperm gaining an extra copy of chromosome 18.

If a reproductive cell with an extra copy of chromosome 18 contributes toward a child’s genetic makeup, they will possess an extra chromosome 18 in each of their body’s cells. If the error in cell division occurs after fertilization of the egg, it is known as mosaic trisomy 18. People with this syndrome will have some cells with two copies of chromosome 18 and other cells with three copies of this chromosome.

In other cases, a person may have partial trisomy 18, which is the only form of trisomy 18 that a person may inherit from a parent. This type occurs due to a genetic change known as a translocation. This term describes a rearrangement of genetic material between chromosomes.

In these cases, a parent may be a carrier of a balanced translocation involving chromosome 18. It is known as a balanced translocation as it does not involve a loss or gain of genetic material. A person with a balanced translocation will not have any signs of trisomy 18 but are more likely to have a child with the condition.

Edwards syndrome typically features a variety of clinical features that can impact all parts of the body. Heart issues, feeding difficulties, and infections often contribute toward poorer outcomes. Signs and symptoms of Edwards syndrome may include:

  • severe intellectual disability
  • low birth weight
  • a small, unusually shaped head
  • a small jaw and mouth
  • clenched fists with overlapping fingers
  • congenital heart issues

Doctors can usually diagnose chromosomal aberrations such as Edwards syndrome before birth. They are able to do so through diagnostic genetic testing.

During the first trimester of pregnancy, a doctor may suggest a chorionic villi sample (CVS). This test involves checking the placenta for tiny finger-like growths known as chorionic villi. These growths contain the same chromosomes as the unborn baby, so they can show if they possess an extra chromosome.

Alternatively, a doctor may suggest analyzing cells in the amniotic fluid, which is known as amniocentesis, during the second or third trimesters. As this fluid contains cells from the fetus, it is possible to study the cells for their chromosome content. Evidence estimates that amniocentesis can give a definitive result in 98–99 out of every 100 people having the test.

After birth, a doctor may be able to diagnose Edwards syndrome by physical examination due to the unique characteristics of the condition. To confirm findings, a doctor can take a blood sample to determine the presence of an extra chromosome 18.

Currently, there is no effective long-term treatment for infants with Edwards Syndrome. Many infants with Edwards syndrome may not survive. In other cases, a doctor may consider an individualized approach depending on which symptoms of the condition are present. This could include:

  • delivery room and neonatal intensive care unit management
  • specialist care
  • feeding management
  • cardiac management
  • orthopedic management
  • psychiatric management
  • treating infections
  • physical therapy

As Edwards syndrome is a severe condition, it is not uncommon for a child to not live beyond the first few years of their life. This means that parents and caregivers may need to consider that the child may never leave the hospital or have a poor quality of life.

However, in individuals with milder symptoms, it is possible for them to survive longer. In this case, they will likely require frequent visits to primary care and specialist doctors. As common symptoms of Edwards syndrome include developmental delays and intellectual disability, a person with the condition will require special care for their entire life.

Organizations that can provide practical information and support for families with a child with trisomy 18 include:

Edwards syndrome refers to a genetic condition where a person has an extra copy of chromosome 18. This is why it is also known as trisomy 18, as an individual has three copies of this chromosome. It typically occurs due to an error with cell division in reproductive cells.

Possessing an extra copy of this chromosome can result in several symptoms, such as intellectual and heart issues. Doctors are able to screen for this condition during pregnancy. As the condition can result in severe developmental issues, many children with the condition may not live beyond the first few years of their life.