Edward Syndrome (Trisomy 18)
What is Edward Syndrome?
Edward syndrome, also known as Trisomy 18, is a rare genetic disorder caused by the presence of an extra copy of chromosome 18. This chromosomal abnormality leads to severe developmental problems and multiple organ defects. The condition was first described by Dr. John Hilton Edwards in 1960.
Edward syndrome is the second most common autosomal trisomy after Down syndrome (Trisomy 21). The extra genetic material disrupts normal development, causing characteristic physical abnormalities, intellectual disability, and serious medical complications. Most infants with Edward syndrome have a shortened lifespan, though the severity can vary depending on the specific type of trisomy 18.
Symptoms of Edward Syndrome
Edward syndrome affects multiple organ systems and causes a wide range of symptoms. The condition is characterized by severe growth retardation and distinctive physical features.
Documented Symptoms
Common Clinical Features
- Low birth weight and growth retardation
- Severe intellectual disability
- Heart defects (present in 90% of cases)
- Kidney abnormalities
- Feeding difficulties
- Breathing problems
Distinctive Physical Features
Facial Features
- Small head (microcephaly)
- Prominent occiput (back of head)
- Low-set, malformed ears
- Small mouth and jaw
- Cleft lip or palate (occasional)
- Eyes that may be cross-eyed or widely spaced
Hand and Foot Abnormalities
- Clenched fists with overlapping fingers
- Index finger overlapping middle finger
- Fifth finger overlapping fourth finger
- Short sternum (breastbone)
- "Rocker-bottom" feet
- Prominent heels
Other Physical Abnormalities
- Short neck
- Chest and pelvic abnormalities
- Hernias (umbilical or inguinal)
- Undescended testicles (in males)
- Spinal abnormalities
- Joint contractures
Organ System Involvement
Cardiovascular System
- Ventricular septal defect (most common)
- Atrial septal defect
- Patent ductus arteriosus
- Complex heart defects
- Heart rhythm abnormalities
Genitourinary System
- Kidney abnormalities (horseshoe kidney)
- Hydronephrosis
- Cryptorchidism (undescended testicles)
- Hypospadias
- Urinary tract malformations
Gastrointestinal System
- Feeding difficulties
- Gastroesophageal reflux
- Intestinal malrotation
- Omphalocele (abdominal wall defect)
- Anal atresia
Nervous System
- Severe intellectual disability
- Developmental delays
- Seizures (occasional)
- Brain malformations
- Hearing loss
Causes and Risk Factors
Genetic Cause
Edward syndrome is caused by the presence of an extra copy of chromosome 18. This can occur in three different ways:
Full Trisomy 18 (95% of cases)
Every cell in the body has three copies of chromosome 18 instead of the normal two copies. This occurs due to nondisjunction during meiosis.
Mosaic Trisomy 18 (less than 5%)
Only some cells have the extra chromosome 18. This results from nondisjunction during early cell division after conception. Symptoms may be less severe.
Partial Trisomy 18 (rare)
Only part of chromosome 18 is present in three copies. This occurs due to chromosomal rearrangements. Symptoms depend on which part is duplicated.
Risk Factors
Maternal Age
The primary risk factor is advanced maternal age, particularly over 35 years. The risk increases significantly with age:
- Age 35: 1 in 2,500 pregnancies
- Age 40: 1 in 1,000 pregnancies
- Age 45: 1 in 400 pregnancies
Other Risk Factors
- Previous pregnancy with trisomy 18 or other chromosomal abnormality
- Parents who are carriers of chromosomal rearrangements
- Exposure to certain environmental factors (limited evidence)
Inheritance Pattern
Edward syndrome is typically not inherited from parents. It usually occurs as a random event during the formation of egg or sperm cells. However, in rare cases of partial trisomy 18 due to chromosomal rearrangements, there may be an increased risk of recurrence in future pregnancies.
Diagnosis
Edward syndrome can be diagnosed before or after birth through various testing methods:
Prenatal Diagnosis
- Maternal Serum Screening: Blood tests to detect increased risk
- Ultrasound: Detection of physical abnormalities
- Cell-free DNA Testing: Non-invasive screening from maternal blood
- Amniocentesis: Analysis of amniotic fluid for chromosomal abnormalities
- Chorionic Villus Sampling (CVS): Testing of placental tissue
Postnatal Diagnosis
- Physical Examination: Recognition of characteristic features
- Chromosomal Analysis (Karyotype): Definitive diagnosis through chromosome study
- FISH Testing: Fluorescence in situ hybridization for rapid results
- Microarray Analysis: Detailed chromosomal analysis
Additional Evaluations
- Echocardiogram: Assessment of heart defects
- Kidney Ultrasound: Evaluation of renal abnormalities
- Brain Imaging: MRI or CT scan for brain abnormalities
- Hearing and Vision Tests: Assessment of sensory function
Prenatal Ultrasound Findings
Common Ultrasound Markers
- Intrauterine growth restriction (IUGR)
- Polyhydramnios (excess amniotic fluid)
- Heart defects
- Clenched fists
- Choroid plexus cysts
- Omphalocele
- Single umbilical artery
- Rocker-bottom feet
Treatment and Management
There is no cure for Edward syndrome. Treatment focuses on supportive care and managing complications to improve quality of life and comfort.
Supportive Care
Medical Management
Therapeutic Interventions
Care Planning Considerations
Families and healthcare teams must make difficult decisions about the extent of medical intervention. Considerations include:
- Overall prognosis and quality of life
- Family values and preferences
- Potential benefits and burdens of interventions
- Comfort and palliative care options
- Support for the entire family
Prognosis and Life Expectancy
Edward syndrome has a poor prognosis, with significant mortality in the first year of life. However, outcomes can vary depending on the specific type and severity of the condition.
Full Trisomy 18
The most severe form with the poorest prognosis:
- 50% of babies do not survive beyond the first week
- 90% do not survive beyond the first year
- Only 5-10% survive to their first birthday
- Very few individuals survive to adulthood
Mosaic Trisomy 18
Generally has a better prognosis than full trisomy:
- Longer survival rates
- Milder intellectual disability
- Less severe physical abnormalities
- Some individuals may reach adulthood
Partial Trisomy 18
Prognosis varies depending on which part of chromosome 18 is involved:
- May have milder symptoms
- Better survival rates
- Developmental delays but potentially longer life expectancy
Factors Affecting Survival
Better Prognosis Associated With
- Mosaic or partial trisomy 18
- Less severe heart defects
- Better feeding tolerance
- Absence of major kidney abnormalities
- Female gender (slightly better survival)
Poorer Prognosis Associated With
- Full trisomy 18
- Severe heart defects
- Significant feeding difficulties
- Major kidney abnormalities
- Severe growth restriction
Family Support and Resources
Families affected by Edward syndrome need comprehensive support and resources:
Medical Support
- Genetic counseling for family planning
- Palliative care specialists
- Pediatric specialists (cardiology, nephrology)
- Social work services
Emotional Support
- Counseling and mental health services
- Support groups for families
- Chaplain or spiritual care services
- Bereavement support
Practical Support
- Financial assistance programs
- Respite care services
- Equipment and supplies
- Home healthcare services
Prevention and Genetic Counseling
While Edward syndrome cannot be prevented, genetic counseling can help families understand risks and make informed decisions:
Genetic Counseling
- Recommended for couples with advanced maternal age
- Important after a previous pregnancy with trisomy 18
- Helpful for understanding recurrence risks
- Provides information about prenatal testing options
Prenatal Care
- Regular prenatal care and monitoring
- Prenatal screening and diagnostic tests
- Detailed ultrasound examinations
- Discussion of family planning options
When to Seek Medical Attention
Contact Healthcare Provider Immediately If:
- Severe breathing difficulties
- Signs of heart failure (blue lips, extreme fatigue)
- Seizures or loss of consciousness
- Signs of severe infection (fever, lethargy)
- Inability to feed or severe feeding difficulties
Schedule an Appointment If:
- Concerns about development or growth
- Need for genetic counseling
- Questions about care planning
- Changes in medical condition
- Need for support services
Medical Disclaimer
This information is for educational purposes only and should not replace professional medical advice. Always consult with a qualified healthcare provider for proper diagnosis and treatment of Edward syndrome or any other medical condition. Genetic counseling is strongly recommended for families affected by or at risk for chromosomal abnormalities.