Chorionic Villus Sampling
The diagnostic procedure of taking out a sample tissue (Choroinic Villi) from the placenta to detect congenital abnormalities in a fetus is known as Chorionic Villus Sampling (CVS). With the guidance of ultrasound, the position of placenta is first determined. There are two methods - trans-cervical and trans-abdominal to perform this test. The position of the placenta helps the physician choose a suitable method. For trans-cervical CVS, parameters like the position of the uterus, the size of the gestational sac and the position of the placenta inside the uterus are first determined using abdominal ultrasound. Using a good antiseptic, the vulva, vagina and the cervix are cleansed. The abdomen is also cleansed for trans-abdominal procedure.
Trans cervical procedure: A thin plastic tube is inserted through the vagina and cervix for the trans-cervical procedure to reach the placenta. A tiny sample of chorionic villus tissue is taken out after locating the exact position of the placenta.
Trans-abdominal procedure: This procedure is similar to the earlier one, but a needle is inserted through the abdomen in this test to reach the uterus and then to the placenta. The chorionic villus sample tissue is drawn into the syringe, while the needle is guided by ultrasound.
This sample is then taken to the laboratory for evaluation. This procedure can be conducted even earlier than amniocentesis to detect any congenital defects present in the fetus. It is done at around 10 to 12 weeks after the last menstruation. Study of the DNA, chromosomes and enzymes of the fetus can be conducted using the sample taken out during the test. Results are available within a week or two. If there are any abnormalities found in the fetus, it is easy to conduct a therapeutic abortion, in case it is necessary. Pregnant women over the age of 35 who are at risk for giving birth to a baby with Downs Syndrome or those who have had birth defects in an earlier pregnancy are advised this test. For detecting neural tube defects and the Rh-incompatibility, amniocentesis is a better option. Hemoglobinopathies and Tay-Sachs disease can be detected through Chorionic Villus Sampling.
The risk involved in using CVS is slightly higher when compared to amniocentesis. Some complications like rupture of the amniotic membrane, miscarriage, infection, bleeding, Rh-incompatibility in the mother if she is Rh-negative and contamination of the sample with maternal cells can occur. When CVS is performed after 10 weeks of gestational period, there is a risk for limb defects in the fetus. If the mother's blood is Rh-negative, she has to receive Rho GAM to avoid Rh incompatibility. After the CVS, it is advised to have an ultrasound done after about two or four days to ensure the fetus is fine.
Turner Syndrome is a condition that affects only girls or women. Most people are born with two chromosomes. While a boy inherits the X chromosome from his mother and Y chromosome from his father, a girl inherits one X chromosome from each parent. In case of Turner syndrome, one copy of the X chromosome is missing or partially missing or is significantly changed.
Named after Henry Turner, the first doctor who reported it in 1938, Turner Syndrome is one of the most common chromosomal disorders and likely the most common genetic disorder of females.
Genetic alterations that causes Turner Syndrome
Monosomy: Complete absence of X chromosome - caused due to an error of father's sperm or in the mother's egg.
Mosaicism: An error that occurs in cell division during early stages of fetal development.
Y chromosome: In a small percentage of Turner Syndrome patients, some cells have only one copy of X chromosome and other cells have one copy of the X chromosome and some Y chromosome material. Though these individuals develop biologically as girls, due to the presence of Y chromosome material increase, the risk of developing a type of cancer called gonadoblastoma is present.
Turner Syndrome can cause a variety of medical problems. Short height, puberty failure, infertility, heart defects and learning disabilities and social adjustment problems are some of the prominent signs of this syndrome. Family history is not a risk factor in this syndrome as it is quite unlikely that parents of one child with this syndrome will have another child with the same disorder.
Prenatal ultrasound of a baby with Turner Syndrome may reveal:
Physical features of Turner Syndrome at birth and during infancy
A wide neck, receding small lower jaw, high narrow roof of the mouth, low-set ears, low hairline behind neck, broad chest with widely spaced nipples, short fingers and toes, arms that turn outward at the elbows, narrow and upward turned fingernails and toes, swelling of hands and feet at birth, smaller than average height at birth and delayed growth.
Physical features noticeable in girls in teens/ young women
There could be occurrences when Turner Syndrome is not quite apparent. Some noticeable features are: No growth spurts, short stature – less than might be expected for a female member of the family, learning disabilities especially that involve spatial concepts or math, inability to understand other people's emotions and social situations, absence of sexual changes expected during puberty due to ovarian failure, early end to menstrual cycles but not due to pregnancy, lack of sexual development during teenage years, inability to conceive a child without fertility treatment.
Sometimes even during fetal development, diagnosis of this syndrome can be made. While ultrasound screening may raise suspicion of Turner Syndrome in the baby; prenatal screening tests that evaluate the baby's DNA in the mother's blood could also indicate an increased risk of this syndrome. Other than the characteristic physical features described above, Turner Syndrome may be diagnosed prenatally, before birth, during infancy or in early childhood, although sometimes the diagnosis might be delayed. It is imperative that girls and women with this syndrome undergo ongoing medical care from a variety of specialists and regular checkups and appropriate care are taken.
Karyotyping is a laboratory test that evaluates the chromosomes which is usually the determining factor for Turner Syndrome. In most cases a blood sample is taken to ascertain a person's karyotype. This syndrome is increasingly diagnosed before birth based on chromosomal analysis subsequent to amniocentesis or Chorionic Villus Sampling CVS. A sample of fluid that surrounds the developing fetus is removed and analyzed. In CVS, it involves the removal of tissue samples from a portion of the placenta. Accumulation of lymph fluid near the neck of a developing fetus can sometimes be seen on a routine fetal ultrasound.
MRI is performed in those affected for the presence of symptoms potentially associated with Turner Syndrome such as liver, kidney and heart abnormalities. Complete cardiac workup including echocardiogram is done to assess the structure and function of the heart. Thyroid and liver function tests, hypertension screening is done. Children and adults require periodic evaluation for hearing also.
Complications arising out of Turner syndrome
Some of the complications arising out of this syndrome include:
Heart defects or slight abnormality in the heart structure that could increase the risk of serious complications. This could be defects in the main blood vessel leading out of the heart or increased risk of a tear in the inner layer of the aorta.
Women with Turner Syndrome can have increased risk of diabetes and high blood pressure. Hearing loss is also common among girls and women with this syndrome. Gradual loss of nerve function could be the reason for hearing loss in some. Slight abnormalities in the shape of the skull could also increase the risk of frequent middle ear infections.
Kidney problems are seen in one-third of girls with Turner Syndrome who have malformation of kidneys. This could increase pressure and urinary tract infections, although they do not necessarily cause medical problems.
Increased risk of certain immune disorders such as hypothyroidism can be seen in some women with this syndrome. This disorder results in low production of hormones that is important for controlling heart rate, growth and metabolism.
Diabetes, inflammatory Bowel Disease and intolerance to wheat are conditions that can be caused by Turner Syndrome. Poor and abnormal tooth development and greater risk of tooth loss or crowded teeth and poorly aligned bite are complications of this syndrome.
Girls with Turner Syndrome pose risk of increased vision problems, due to weak muscle control of eye movements and farsightedness. Bones are bound to get affected by this syndrome, with increased risk of abnormal curvature of the spine and forward rounding of the upper back. Osteoporosis is another common risk of this syndrome.
Though most women with this syndrome are infertile, a small number do get pregnant spontaneously, and others become pregnant with fertility treatment. But, there are instances where women with this syndrome are likely to experience failure of the ovaries and subsequent infertility very early in adulthood. A cardiologist intervention is essential before pregnancy as they are at increased risk of aortic dissection during pregnancy. They are also at increased risk of high blood pressure and gestational diabetes during pregnancy.
Some girls and women do have psychological issues due to Turner Syndrome with disabilities in math and spatial concepts, difficulties in social situations and increased risk of attention-deficit/hyperactivity disorder.
Treatment and medication
Since chromosomal abnormality causes this syndrome, as such there is no specific cure. However, researchers have developed a number of treatments that can help with growth problems. Growth hormone therapy is recommended for most girls with this syndrome. This is done to increase height as much as possible at appropriate times during childhood and teen years. Growth hormone is given by way of injections several times a week and if the height is really short, doctors recommend androgens in addition to growth hormone.
Estrogen therapy is administered in order to begin puberty and achieve adult sexual development. Estrogen is also given along with growth hormone. Estrogen therapy usually continues throughout life until average age of menopause.
In case of some women with Turner Syndrome, they can become pregnant with donation of an egg or embryo. A specially designed hormone therapy is necessary to prepare the uterus for pregnancy. And pregnancy can be high-risk with Turner Syndrome.
Management of Turner syndrome
Those affected are advised regular checkups which can improve the quality and length of life. Periodic checkups for hearing loss, eye problems, high blood pressure and diabetes and osteoporosis are imperative. Follow-up with a heart specialist is essential as are regular ultrasounds of the heart. Healthy lifestyle habits such as maintaining proper weight and exercising regularly are important throughout life.
And, although girls with Turner syndrome exhibit learning disabilities, most can attend school regularly, write well, learn by hearing, can memorize and develop reasonably good language skills.
Tips for those with Turner syndrome
Tay Sachs Disease
Tay-Sachs disease is a fatal genetic disorder that causes gradual deterioration of the central nervous system. Tay-Sachs disease is normally noticed in infants. Important enzymes such as Hexosaminidase A (Hex A) are responsible for removing the fatty substances in the brain to facilitate the growth in the baby. These enzymes also help the infants to develop vision, hearing, movement and such other important functions of the body. Absence of this vital enzyme leads to Tay-Sachs disease. High amount of a fatty substance called ganglioside builds up in tissues and nerve cells of the brain. Defects in a gene on chromosome 15 that facilitates production of the enzyme Hex-A.
This is a genetic disorder. Both parents must be carriers for the child to be affected. When both the parents are carriers there is a 1 in 4 chance that their child will inherit a Tay-Sachs gene. In few of the cases, children may just become carriers and not have the disease. There is also 25% chance that, when both the parents are carriers, the child will not be a carrier and not have the disease. Tay-Sachs disease normally occurs in infants. Very rarely the symptoms begin in later childhood or adolescence and adulthood. Most children with Tay-Sachs disease usually die before reaching the age of five.
This disease is normally found in the people of Ashkenazi (eastern and central European) Jews. It is also found in French-Canadian communities of Quebec, the Old Order Amish community in Pennsylvania, and the Cajun population of Louisiana.
Signs and Symptoms of Tay-Sachs
The signs and symptoms of the Tay-Sachs differ according to the onset of the disease. Infants with Tay-Sachs disease appear to develop normally for the first few months of their life. It is only after 5 or 6 months, that gradually baby loses the vision, ability to hear, and move. A red spot develops in the back of the child's eyes. The child experiences loss of motor skills like crawling, turning over, and reaching out for things. As the child ages, he/she may suffer from seizures, mental retardation, paralysis and become completely disabled. Death usually occurs by the time the child is 5 years old.
One more form of Tay-Sachs disease is adult-onset. It is rare to find this form of the disease. Symptoms of Tay-Sachs disease for late onset include muscle weakness, loss of muscle coordination, difficulty in movement, speech problems and even mental illness.
Apart from studying the symptoms, family history, a simple blood test is conducted to assess the level of Hex-A in a person's blood. Carriers have less Hex-A in their body fluid and cells than non-carriers.
Expectant mothers can go for prenatal testing for Tay-Sachs around the 11th week of pregnancy through chorionic villi sampling (CVS). Between the 15th and 18th weeks of pregnancy, fetus can be tested with amniocentesis for the Tay-Sachs gene.
Treatment for Tay-Sachs
Presently, there is no cure or effective treatment for Tay-Sachs. Few anticonvulsant medicines are prescribed to control seizures. Patients with Tay-Sachs tend to get dehydrated easily, hence sufficient amount of fluids is recommended along with proper nutrition. Special care also needs to be taken to keep the airways open.
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Bibliography / Reference
Collection of Pages - Last revised Date: December 13, 2019