A rare disease is defined as a condition that affects fewer than 200,000 people in the United States. Trisomy 18, also known as Edwards syndrome, is a rare genetic condition that falls within this category. It occurs when an extra copy of chromosome 18 is present in some or all of the body’s cells. This additional genetic material can disrupt typical development, often resulting in significant medical and developmental challenges. Trisomy 18 affects approximately 1 in 5,000 live births.
Trisomy 18 Common Characteristics and Complications
Children and individuals with Trisomy 18 may experience a wide range of physical and intellectual disabilities. Common features include:
- Developmental Delays: Slowed growth and challenges in motor, cognitive, and physical development.
- Craniofacial Differences: Features such as a small head (microcephaly), a small jaw (micrognathia), low-set ears, a prominent occiput (back of the head), and sometimes cleft lip or palate.
- Heart Defects: Many infants are born with congenital heart conditions that may require urgent medical care or surgical intervention.
- Kidney and Urinary Tract Issues: These can cause additional medical complications.
- Skeletal Abnormalities: Common signs include clenched fists with overlapping fingers, clubfoot, and “rocker-bottom” feet (rounded soles).
- Gastrointestinal Disorders: Conditions such as esophageal atresia (a disconnection between the esophagus and stomach) may occur.
- Respiratory Challenges: Weak muscles and structural differences often contribute to breathing difficulties.
- Intellectual Disabilities: Cognitive impairments typically range from moderate to severe.
Types of Trisomy 18
There are three known types:
- Full Trisomy 18: Every cell in the body contains an extra chromosome 18. This is the most common and typically the most medically complex form.
- Mosaic Trisomy 18: Only some of the body’s cells carry the extra chromosome. Symptoms may be milder and survival longer, depending on the distribution of affected cells.
- Partial Trisomy 18: A portion of chromosome 18 is attached to another chromosome. This rare type can sometimes be inherited and presents with a wide range of outcomes.
Prognosis and Survival
Trisomy 18 is a condition associated with high rates of miscarriage and infant mortality. For those born alive:
- 60%–75% survive the first week.
- 20%–40% survive the first month.
- About 5%–10% live beyond their first birthday.
While historically survival rates have been very low, advances in medical care and greater recognition of treatment options have led to more children living into childhood, adolescence, and even adulthood. Each child’s journey is unique, with outcomes shaped by the type of Trisomy 18, the severity of medical complications, and access to timely, coordinated, and compassionate care.
Diagnosis and Inheritance
Prenatal diagnosis is possible through procedures such as amniocentesis or chorionic villus sampling (CVS), which can detect the presence of an extra chromosome 18.
- Full and Mosaic Trisomy 18 usually occur as random events caused by errors during the formation of eggs or sperm (nondisjunction).
- Partial Trisomy 18 may be inherited. In these cases, a parent may carry a balanced translocation involving chromosome 18 without showing any symptoms.
Community Conversations
Understanding Trisomy 18: A Spotlight on Community Conversations is a compilation of videos highlighting the personal stories and advocacy journeys of parents, caregivers, clinicians, and individuals living with Trisomy 18. This resource amplifies lived experiences, offering education, hope, and a platform for advocacy.
*🎥 Some videos are provided courtesy of E.WE Foundation partners.
Source: U.S. National Library of Medicine. Medline Plus. http://www.medlineplus.gov | Centers for Disease Control and Prevention. http://www.cdc.gov | Cleveland Clinic. http://www.my.clevelandclinic.org
The E.WE Foundation 