Genetics
Trisomy 18 or Edwards Syndrome is a genetic disorder caused by the presence of an extra copy of all or part of chromosome 18. The extra chromosome 18 is retained because of a nondisjunction event during meiosis. The incidence increases as the mother’s age increases. The syndrome has a very low rate of survival, resulting from heart abnormalities, kidney malformations, and other internal organ disorders.
Incidence
One in 3,000 pregnancies and approximately one in 6,000 live births
Symptoms/Characteristics
In utero, the most common characteristic are
- cardiac anomalies
- central nervous system anomalies
- choroid plexus cysts
- polyhydramnios
All infants born with Edwards syndrome present with
- kidney malformations
- Structural heart defects
- Omphalocele
- Esophageal atresia
- Mental retardation
- Developmental delays
- Growth deficiency
- Feeding difficulties
- Breathing difficulties
- Arthrogryposis
Some other physical finding may include
- Short breast bone
- Clenched hands
- Underdeveloped thumbs and or nails
- Absent radius
- Webbing of the second and third toes
- Clubfoot or Rocker bottom feet
- Undescended testicles in males.
Facial Features
- Microcephaly accompanied by a prominent back portion of the head
- Low-set, malformed ears
- abnormally small jaw (micrognathia)
- Cleft lip/cleft palate
- Upturned nose
- Narrow eyelid folds (palpebral fissures)
- Widely-spaced eyes (ocular hypertelorism)
Clinical Management
The survival rate of Edwards Syndrome is very low. About 95% die in utero. Of liveborn infants, only 50% live to 2 months, and only 5–10% will survive their first year of life. Major causes of death include apnea and heart abnormalities. It is impossible to predict the exact prognosis of an Edwards Syndrome child during pregnancy or the neonatal period. Because major medical interventions are routinely withheld from these children, it is difficult to determine what the survival rate or prognosis would be with aggressive medical treatment. The median life span is five to fifteen days. One percent of children born with this syndrome live to age ten, typically in cases of the less severe, mosaic Edwards syndrome.