trisomy 18 genetic disorder

3 min read 12-03-2025

Trisomy 18, also known as Edwards syndrome, is a rare chromosomal condition that occurs when a person has three copies of chromosome 18 instead of the usual two. This extra genetic material disrupts normal development, leading to a range of physical and intellectual challenges. Understanding Trisomy 18 is crucial for families affected by it and for healthcare professionals providing care.

What Causes Trisomy 18?

Trisomy 18 happens during the formation of reproductive cells (eggs and sperm). An error in cell division called non-disjunction results in a sperm or egg cell with an extra copy of chromosome 18. When this abnormal cell is involved in fertilization, the resulting embryo has three copies of chromosome 18 in all its cells. This is the most common cause. Less frequently, mosaic trisomy 18 occurs, where some cells have the extra chromosome while others have the normal number. This typically leads to a milder presentation of the condition. There is no known way to prevent Trisomy 18.

Common Characteristics of Trisomy 18

Trisomy 18 presents with a wide range of characteristics, and severity varies significantly between individuals. Some common features include:

Low birth weight and small size: Babies with Trisomy 18 are often born smaller than average.
Heart defects: Congenital heart defects are common and often serious.
Kidney problems: Kidney malformations can also occur.
Clenched fists with overlapping fingers: This is a characteristic feature often noted at birth.
Low-set ears: Ears are typically positioned lower on the head than normal.
Developmental delays: Significant developmental delays in both motor skills and cognitive abilities are common.
Feeding difficulties: Babies may have trouble feeding due to weak muscle tone and other physical challenges.
Breathing problems: Respiratory issues can arise from underdeveloped lungs or other complications.
Intellectual disability: Individuals with Trisomy 18 typically experience intellectual disability.

Diagnosis and Testing for Trisomy 18

Prenatal diagnosis is possible through several methods:

Ultrasound: An ultrasound can reveal structural abnormalities suggestive of Trisomy 18 during pregnancy.
Chorionic villus sampling (CVS): This procedure involves taking a sample of placental tissue to analyze the chromosomes.
Amniocentesis: This involves taking a sample of amniotic fluid to analyze fetal cells.
Non-invasive prenatal testing (NIPT): A blood test that analyzes cell-free fetal DNA in the mother's blood. This is a less invasive option with high accuracy.

After birth, a physical examination and genetic testing (karyotype) will confirm the diagnosis.

How is Trisomy 18 Treated?

Unfortunately, there's no cure for Trisomy 18. Treatment focuses on managing symptoms and providing supportive care to improve the child's quality of life. This includes:

Medical management of heart defects: Cardiac surgery may be necessary to correct congenital heart problems.
Respiratory support: Ventilator support might be needed for breathing difficulties.
Feeding assistance: Feeding tubes may be required to ensure adequate nutrition.
Physical and occupational therapy: Therapy helps improve motor skills and development.
Developmental support programs: Early intervention programs are crucial for promoting development.
Palliative care: For infants with severe cases, palliative care focuses on comfort and pain management.

Prognosis and Life Expectancy for Trisomy 18

The prognosis for Trisomy 18 is variable. Many babies with Trisomy 18 are stillborn or die within the first few weeks or months of life due to severe health complications. Those who survive infancy often experience significant developmental delays and may face life-long health challenges. While some individuals with mosaic Trisomy 18 may live longer and have a milder phenotype, the majority will experience significant health issues. The average life expectancy for infants with Trisomy 18 is quite low.

Support and Resources for Families

A diagnosis of Trisomy 18 can be devastating. Families need significant emotional and practical support. Organizations such as the Trisomy 18 Foundation offer invaluable resources, including:

Information and education: Learn more about Trisomy 18 and its management.
Support groups: Connect with other families facing similar challenges.
Advocacy: Work to improve resources and understanding of the condition.

Disclaimer: This article is intended for informational purposes only and should not be considered medical advice. Consult a healthcare professional for any health concerns or before making any decisions related to your health or treatment.