Edward’s Syndrome or Trisomy 18: Definition, Manifestations, and Treatment.
Definition
Edwards Syndrome is also known as Trisomy 18 (T18) or Trisomy E. It
is a genetic disorder caused by the presence of all or part of an extra
18th chromosome. The majority of people with the syndrome die during the
fetal stage; infants who survive experience serious defects and
commonly live for short periods of time. Edwards’ syndrome is associated
with a broad spectrum of abnormalities which consist of greater than
one-hundred and thirty discrete defects involving the brain, heart,
craniofacial structures, kidneys and stomach.
History
John Hilton Edwards first described the symptoms of the genetic
disorder known as Trisomy 18-one of the most common forms of human
trisomy, which occurs when cells have an extra copy of a chromosome, in
1960. Trisomy 18, also known as Edwards Syndrome, occurs approximately
once per 6000 live births and is second in frequency only to Trisomy 21,
or Down’s syndrome, as an autosomal trisomy. Trisomy 18 causes
substantial developmental problems in utero.
Types of Trisomy 18
- Full trisomy 18. The extra chromosome is in every cell in the baby’s body. This is by far the most common type of trisomy 18.
- Partial trisomy 18.The child has only part
of an extra chromosome 18. That extra part may be attached to another
chromosome in the egg or sperm (called a translocation). This type of
trisomy 18 is very rare.
- Mosaic trisomy 18. The extra chromosome 18 is only in some of the baby’s cells. This form of trisomy 18 is also rare.
Symptoms and signs
Babies with trisomy 18 are often born very small and frail. They
typically have many serious health problems and physical defects,
including:
- Cleft palate
- Clenched fists with overlapping fingers
- Defects of the lungs, kidneys, and stomach/intestines
- Deformed feet (called “rocker-bottom feet”)
- Feeding problems
- Heart defects, including a hole between the chambers
- Low-set ears
- Neurodevelopmental delays Chest deformity
- Small head (microcephaly)
- Small jaw (micrognathia)
- short sternum
- Weak cry
Diagnosis and Testing
In most cases trisomy 18 are diagnosed prenatally.
- Standard pregnancy screening during the first and second trimesters
including serum markers (plasma protein, beta-hCG, alpha-fetoprotein,
unconjugated estriol, and inhibin A) with ultrasound (nuchal
translucency and other anatomic abnormalities) can accurately diagnose
more than three quarters of all cases.
- Potential tests include maternal serum alpha-fetal protein analysis or screening, ultrasonography, amniocentesis
- Chorionic villi sampling (CVS) is another genetic-based test that can diagnose trisomy 18.
- Definitive diagnosis is achieved through karyotyping, which involves
drawing the baby’s blood for a microscopic examination of the
chromosomes. Using special stains and microscopy, individual chromosomes
are identified, and the presence of an extra chromosome 18 is revealed.
- In addition, a pregnant woman carrying a child with Edwards’
syndrome may have an unusually large uterus during pregnancy, due to the
presence of extra amniotic fluid (polyhydramnios). An unusually small
placenta may be noted during the birth of the child.
- After birth, the doctor may suspect trisomy 18 based on the child’s
face and body. A blood sample can be taken to look for the chromosome
abnormality.
Treatment and medications
- There is no cure for trisomy 18. Treatment for trisomy 18 consists
of supportive medical care to provide the child with the best quality of
life possible.
- Constipation due to poor abdominal muscle tone is often a life-long
problem for babies and children with Edwards’ syndrome, resulting in
fretfulness, discomfort, and feeding problems. Anti-gas medication,
special milk formulas, stool softener medicines, laxatives, and
suppositories are all possible treatments that the doctor may recommend
to ease the discomfort of gas in the bowels or constipation.
Trisomy 18 Prognosis and Life Expectancy
- Due to the presence of several life-threatening medical problems,
many infants with trisomy 18 die within their first month. Five percent
to 10 percent of children with this condition live past their first
year.
Prevention
Most cases of Edwards’ syndrome are not hereditary and cannot be
prevented. However, parents who have had a child with Edwards’ syndrome
are at increased risk of having another child with the syndrome.
Prognosis
- 50% of children born with this disorder do not survive the 1st week of life
- most die before 1 year of age
- some cases have been reported on children surviving into teenage years, though with multiple medical problems
