Edwards%26rsquo; syndrome is caused by an extra copy of chromosome 18, which is why it is also called Trisomy 18 syndrome. The extra chromosome is lethal for most babies born with this condition and it causes major physical abnormalities and severe mental retardation. Very few children afflicted with this disease survive beyond a year. Although we do not know how many babies die we could say it is a problem we should know about.About chromosomes
There are 23 pairs of human chromosomes, and in Trisomy 18 or Edwards syndrome, there is an extra chromosome with the 18th pair. Like Trisomy 21 known as Down syndrome, Trisomy 18 affects all systems of the body and causes distinct facial features. It is estimated to occur in 1 in 6,000-8,000 live births, where unfortunately, about 95% of fetuses die before birth. Therefore, the actual incidence of the disorder may be higher. Of those born, approximately 80% are females although Trisomy 18 affects individuals of all ethnic backgrounds and both sexes. Humans normally have 23 pairs of chromosomes and these chromosomes are numbered 1-22. The 23rd pair is composed of the sex chromosomes, X and Y. A person inherits one set of 23 chromosomes from each parent, so occasionally, a genetic error occurs during egg or sperm cell formation. A child conceived with such an egg or sperm cell may inherit an incorrect number of chromosomes.
As you already heard, in the case of Edwards' syndrome, the child inherits three, rather than two, copies of chromosome 18. Trisomy 18 occurs in approximately one in every 3,000 newborns and affects girls more often than boys, where women older than their early thirties have a greater risk of conceiving a child with Trisomy 18, but it can occur in younger women.
Symptoms of Trisomy 18
A third copy of chromosome 18 causes numerous abnormalities, where most children born with Edwards' syndrome appear weak and fragile, often underweight.
The head is unusually small and the back of the head is prominent, the ears are malformed and low-set, and the mouth and jaw are small. The baby may also have a cleft lip or cleft palate, and frequently, the hands are clenched into fists, and the index finger overlaps the other fingers. The child may have clubfeet and toes may be webbed or fused as well. Numerous problems involving the internal organs may be present with abnormalities often occurring in the lungs and diaphragm, and heart defects and blood vessel malformations are common. The child may also have malformed kidneys and abnormalities of the urogenital system as well.
Trisomy 18 severely affects all organ systems of the body, so the symptoms could be various. Symptoms may include different body systems, and are typical for each system.
* Nervous system and brain: mental retardation and delayed development 100% of individuals, high muscle tone, seizures, and physical malformations such as brain defects.
* Head and face: small head (microcephaly), small eyes, wide-set eyes, epicanthal folds, small lower jaw.
* Heart: congenital heart defects at 90% of individuals, such as ventricular septal defect and valve defects.
* Bones: severe growth retardation, clenched hands with 2nd and 5th fingers on top of the others, and other defects of the hands and feet.
* Malformations of the digestive tract, the urinary tract, and genitals of these patients is common as well.
Diagnosis
Physical abnormalities point to Edwards' syndrome, but a definitive diagnosis relies on karyotyping, which involves drawing the baby%26rsquo;s blood or bone marrow for a microscopic examination of the chromosomes. Using special stains and microscopy, individual chromosomes are identified. It is valuable that the presence of an extra chromosome 18 could be revealed. It is very good what Trisomy 18 can be detected before birth. If a pregnant woman is older than 35, has a family history of genetic abnormalities, has previously conceived a child with a genetic abnormality, or has suffered earlier miscarriages, she may undergo tests. It is important to determine whether her child carries genetic abnormalities. Potential tests include maternal serum analysis or screening, ultrasonography, amniocentesis, and chorionic villus sampling, depending on the woman%26rsquo;s and her doctor%26rsquo;s decision.
Treatment for Trisomy 18
Unfortunately, there is no cure for Edwards%26rsquo; syndrome. Since Trisomy 18 babies frequently have major physical abnormalities, doctors and parents face difficult choices regarding treatment. Abnormalities can be treated to a certain degree with surgery, but extreme invasive procedures may not be in the best interests of an infant, since an infants%26rsquo; lifespan is commonly measured in days or weeks. Medical therapy often consists of supportive care with the goal of making the infant comfortable, rather than prolonging their life. That is why we say that medical care for individuals with Trisomy 18 is supportive.
The treatment focuses on providing nutrition, treating infections, and managing heart problems. During the first months of life, infants with Trisomy 18 require skilled medical care, due to the complex medical problems. Because of heart defects and overwhelming infections, infants have a 5% chance of surviving to the age of one. Advances in medical care over time will, in the future, help more infants with Trisomy 18 live into childhood and beyond of it.
Prognosis
Most children born with Trisomy 18 die within their first year of life, with an average lifespan of under two months for 50% of the children, and 90-95% die before their first birthday. The 5-10% of children who survive their first year are severely mentally retarded and they need support to walk, and their learning is limited as well. Verbal communication is also limited, but they can learn to recognize and interact with other people. It is also important to point out that Edwards%26rsquo; syndrome or Trisomy 18 cannot be prevented.
Tests for detecting Trisomy 18 before birth
* Aminocentesis is a procedure in which a needle is inserted through a pregnant woman%26rsquo;s abdomen and into her uterus to withdraw a small sample of amniotic fluid. This fluid can be examined for signs of disease or other problems afflicting the fetus.
* Chorionic villus sampling test is best done during weeks 10-12 of a pregnancy. The procedure involves inserting a needle into the placenta and withdrawing a small amount of the chorionic membrane for analysis of fetuses%26rsquo; gene.
* Karyotyping is a laboratory test used to study an individual%26rsquo;s chromosome make-up. Chromosomes are separated from cells, stained, and arranged in order from largest to smallest. This way their number and structure can be studied under a microscope.
* Maternal serum analyte screening is a medical procedure in which a pregnant woman%26rsquo;s blood is drawn and analyzed for the levels of certain hormones and proteins. These levels can indicate whether there may be an abnormality in the unborn child or not. This test is not a definitive indicator of a problem and it should be followed by more specific testing such as amniocentesis or chorionic villus sampling.
* Ultrasound is a medical test also known as ultrasonography. Sound waves are directed against internal structures in mother%26rsquo;s body. As sound waves bounce off the internal structure, they create an image on a video screen and ultrasound of a fetus at weeks 16-20 of a pregnancy can be used to determine structural abnormalities. The features and problems children with Edward%26rsquo;s syndrome develop vary from child to child but typically a child will have most of these symptoms you have already hear. In addition to these characteristic features, all systems of the body may be affected.
Medical problems and complications due to Trisomy 18
The increased occurrence of infant mortality is related to a combination of factors. However, most importantly the problem is central apnea, where the brain does not give the message to breathe. Other complicating factors include difficulty feeding with aspiration with a predisposition to aspiration pneumonia, and under development of the lungs as one of important symptoms for Trisomy 18. Heart defects can play some role in this but are usually not the only cause of this increased mortality. Infection is an ongoing medical concern is one of the most common complications that occur in patients with Trisomy 18 or Edwards%26rsquo; syndrome. Infections are usually secondary to otitis media, upper respiratory tract infections, and urinary tract infections as well. Scoliosis secondary to hemivertebra is a common finding, as well as feeding problems, which are major management issue. Congenital heart defect with congestive heart failure is a frequent cause of death of patients diagnosed with Edwards%26rsquo; syndrome. Wilms tumor may develop in long-term survivors with Trisomy 18 as well.
It is important to provide care for these patients, such as cardiac management, which is primarily medical. Providing gastrostomy for feeding problems is also important. Outpatient care are nasogastric or gastrostomy feeding, orthopedic care of scoliosis, audiologic evaluation for hearing loss, and apnea monitoring. In and out patient meds are diuretics and digoxin. These drugs may be used to manage congestive heart failure secondary to congenital heart defect caused by Trisomy 18 or Edwards%26rsquo; syndrome.
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