Introduction
Chromosomes are filamentous structures of nucleic acids and proteins that are present in the nucleus of living cells and are responsible for carrying genetic information in the form of genes. Chromosomal aberrations usually occur when there are faults in cell division, resulting in cells with too few or too many copies of chromosomes. Normally, during gamete formation, two pairs of chromosomes (one from the mother and one from the father) separate in a process called meiosis. This leaves only one copy of each chromosome in the gamete (as opposed to the two copies found in other body cells). Errors in this segregation process result in the formation of gametes with an incomplete set of chromosomes or extra whole or partial chromosomes. This is known as meiotic nondisjunction.
What Is Meant by Tetrasomy X and Pentasomy X Females?
Tetrasomy X and pentasomy X are rare sex chromosomal abnormalities. These conditions affect only females, whereby two and three additional X chromosomes are added respectively to the two normally present X chromosomes in females. Even minor changes in chromosomal structure can affect multiple genes and can have profound effects.
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Tetrasomy X - Tetrasomy X is also known as XXXX syndrome, Tetra X, 4 times X, or 48 XXXX. It only affects girls. The genes that direct the development and function of the body are correctly arranged along the chromosome. There are usually 46 chromosomes, 22 pairs numbered 1 to 22 plus 2 sex chromosomes. Male gender chromosomes are different: one is called X, and the other is called Y, the male chromosome is usually written as 46, XY. Females typically have two X chromosomes; they are listed as 46 XX. Tetrasomy X girls have four copies of the X chromosome that make up the chromosome description (karyotype) 48 XXXX.
Tetrasomy X is not generally inherited but occurs through a random event called nondisjunction during gamete or zygote development. The formal term for the karyotype observed in tetrasomy X is 48 XXXX. This is because the condition is characterized by a 48-chromosome complement rather than the 46 observed in normal human development.
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Pentasomy X - Pentasomy X, also known as 49 XXXXX, is a chromosomal abnormality in which females have five X chromosomes instead of two.
What Are the Causes of Tetrasomy X and Pentasomy X Syndromes?
A woman with tetrasomy X inherits three X chromosomes from her mother, one X from her father, or all four X chromosomes from her mother. During the formation of the mother's eggs or chromosome pairs, they usually divide to contain a single X chromosome. The error is repeated from cell to cell, and division can leave each egg with three or four more X chromosomes. When a sperm with an X fertilizes it, the egg contains two extra X chromosomes. Few people then grow up to have a baby with four X chromosomes or start life with five X chromosomes. In rare cases, other processes may be involved, such as errors in cell division after conception (at birth or conception of the baby) due to the presence of some X chromosomes in maternal cells.
What Are the Risk Factors for Tetrasomy X and Pentasomy X Syndromes?
The risk factors of chromosomal abnormalities are listed below:
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Age - The older aged woman is more likely to have offspring with a chromosomal abnormality.
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Genetics - A family history of genetic abnormalities.
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History - A previous baby with a birth defect or miscarriage and a chromosomal abnormality in one of the prospective parents.
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Exposure to Toxins - Repeated exposure to toxins may result in an elevated risk of chromosomal abnormalities.
What Are the Symptoms of Tetrasomy X and Pentasomy X Syndromes?
The signs and symptoms of tetrasomy X and pentasomy X syndromes may vary in each case. The signs and symptoms found in them are listed below:
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Short stature.
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Intellectual disability.
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Heart defects.
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Skeletal anomalies.
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Pubertal and reproductive abnormalities.
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Mild to moderate speech and learning difficulties.
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Developmental delay.
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Distinctive facial features.
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Dental abnormalities.
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Hypotonia and joint laxity (decreased muscle tone).
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Radioulnar synostosis (radius and ulna abnormally connected).
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Hip dysplasia.
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Problems with ovarian function.
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An increased risk of childhood infections.
How Are Tetrasomy X and Pentasomy X Syndromes Diagnosed?
Chorionic Villus Sampling (CVS) - It is a prenatal test in which a sample of tissue is removed from the placenta to test for chromosomal abnormalities and certain other genetic problems. The placenta is a structure within the uterus that supplies blood and nutrients from the mother to the fetus. Chorionic villi are tiny projections of placental tissue that resemble fingers and are composed of the same genetic material as the fetus. CVS is normally done between 10 and 12 weeks of pregnancy. There are two types of CVS procedures which are as follows:
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Transcervical - In this procedure, a tissue sample is taken by inserting a catheter through the cervix and into the placenta.
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Transabdominal - Transabdominal procedure involves the insertion of a needle through the abdomen and uterus and then into the placenta, and a tissue sample is taken.
Amniocentesis - It is performed to remove amniotic fluid and cells from the uterus for examination or treatment. Amniotic fluid envelops and protects the baby during pregnancy.
This procedure gives crucial information about the genetic makeup of the fetus and chromosomal abnormalities. This procedure has its own risks, and informed consent of the patient is needed to perform this procedure. The risks associated with this procedure are mentioned below:
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Leaking amniotic fluid.
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Miscarriage.
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Needle injury to the fetus.
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Uterine infection.
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HIV and hepatitis infection transmission from mother to fetus.
What Is the Treatment for Tetrasomy X and Pentasomy X Syndromes?
There is no cure for these abnormalities. The aim is to relieve symptoms and improve quality of life. How this is done depends on the person's anomaly or problem. For example, structural problems such as heart defects can be corrected through surgery. Young children can benefit from early interventional services. Older children may require special education needs. Some adults lead active lives. Some people live with their families, and others live alone.
How to Prevent Tetrasomy X and Pentasomy X Syndromes?
This condition is not 100 % preventable, but certain measures can be taken to lower the risk of babies acquiring this condition. One must consult a doctor three months before conception to discuss health issues and medications.
Also, one must take a daily prenatal vitamin containing 400 micrograms of folic acid three months before conception. Other prevention measures include:
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Eating a healthy diet that includes folate-containing foods such as breakfast cereals, grain products, leafy greens, oranges, orange juice, and peanuts.
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Achieving or maintaining a healthy weight.
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Avoiding smoking and alcohol.
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Avoiding substance abuse.
Conclusion
Chromosomal abnormalities can be quite overwhelming to deal with, particularly when accompanied by symptoms that could signifcantly decrease the quality of life. Tetrasomy X and pentasomy X are two such examples that of disorders characterized by alterations of the sex chromosomes in females due to faulty DNA replication. The condition can be limiting in its severity. However, while it is not preventable, it can be managed. No treatment is available for this condition. Genetic testing can be done to ascertain the presence of such a syndrome in one’s baby, and decisions or further steps can be taken accordingly.
