What Is Trisomy 18?
Trisomy 18 (also called Edwards syndrome) is a condition that occurs when there is an error in cell division called meiotic disjunction.
When meiotic disjunction occurs, instead of a normal pair of chromosomes, an extra chromosome 18 occurs (a triple) in a developing baby which disrupts normal development in significant ways that can be life-threatening, even before birth.
Trisomy 18 (also called Edwards syndrome) is a condition that occurs when there is an error in cell division called meiotic disjunction. When meiotic disjunction occurs, instead of a normal pair of chromosomes, an extra chromosome 18 occurs (a triple) in a developing baby which disrupts normal development in significant ways that can be life-threatening, even before birth.
Trisomy 18 is associated with more medical complications that are more potentially life-threatening than Down syndrome, another condition caused by an extra chromosome.
What Are Symptoms of Trisomy 18?
Symptoms of Trisomy 18 are numerous and can include:
- Opening in the wall separating the top two chambers of the heart (atrial septal defect)
- Broad forehead
- Wasting syndrome
- Permanent flexion or atypical position of the finger
- Cognitive impairment
- Undescended testes
- Long, narrow head
- Developmental delay
- High forehead
- Wide-set eyes
- Muscle spasticity
- Prenatal growth deficiency
- Low-set ears that turn toward the back of the head
- Small receding chin
- Low or weak muscle tone
- Narrow face, mouth, and palate
- Narrow pelvis bone
- Organs protrude from the belly button at birth
- “Spock's ear”
- Prominent back of the skull
- Short nose
- Short stature
- Face with broad temples and narrow chin
- Flattened bony protrusion above eyes
- Hole in heart wall separating two lower heart chambers (ventricular septal defect)
- Abnormal formation of internal female genitalia
- Abnormality of the toenail
- Abnormality of the fontanelles or cranial sutures
- Abnormality of the hips
- Absent anus
- Narrow opening between the eyelids
- Blockage of the rear opening of the nasal cavity
- Cleft palate
- Non-midline cleft lip
- Congenital diaphragmatic hernia
- Delayed bone maturation
- Eye folds
- Birth defect in which part of esophagus did not develop
- Kidney swelling
- Abnormally small skull
- Webbed neck
What Causes Trisomy 18?
Trisomy 18 is caused by an error that occurs in cell division called meiotic disjunction, which results in a baby having 3 copies of chromosome 18 in each cell in the body, instead of the usual 2 copies. The extra copy of the chromosome interferes with development in significant ways.
How Is Trisomy 18 Diagnosed?
What Is the Treatment for Trisomy 18?
There is no specific treatment for Trisomy 18, and the condition cannot be cured. Instead, treatments are aimed at management of symptoms and may include:
- Treating infections when they occur
- Nasogastric and gastrostomy supplementation for feeding problems
- Orthopedic management of scoliosis
- Cardiac management
- Neonatal intensive care (NICU) management
- NICU management is controversial because of the poor prognosis and the lack of effectiveness of treatment
- Genetic counseling
- Psychosocial management
- Educating parents about the syndrome
- Support services for the family
- Grief counseling
- Because Trisomy 18 has such a poor prognosis, some types of surgical repair for severe congenital anomalies may not be considered
What Is the Life Expectancy for Trisomy 18?
There is a high mortality rate for children with Trisomy 18 before or shortly after birth. Only about 50% of babies carried to term are born alive. Baby girls have higher rates of live birth than baby boys.
Some infants may survive to be able to be discharged from the hospital with home nursing care.
About 10% or more may survive one year, and a small number of adults (usually females) with Trisomy 18 have lived into their twenties and thirties, although they have significant developmental delays and require full-time care.