Triploidy: what is it, causes, symptoms, prognosis

What is Triploidy?

Triploidy - a rare chromosomal abnormality. Triploidy is the presence of an additional set of chromosomes in a cell, a total of 69 chromosomes, and not 46 ordinary chromosomes per cell. The extra set of chromosomes comes either from the father or from the mother during fertilization. Pregnancy with triploidy usually ends in miscarriage in early pregnancy. If the pregnancy remains full-term, the baby dies in the first days of life. Several affected individuals were reported to have survived to adulthood but suffered from developmental delays, learning difficulties, epilepsy, hearing loss, and other anomalies. Survivors have mosaic triploidy, which means that some cells have a normal number of chromosomes of 46, while other cells have 69 chromosomes per cell.

Signs and symptoms

Triploidy babies have heart defects, brain abnormalities, defects 

adrenal glands and kidney (cystic kidney damage), spinal cord malformations (neural tube defects), and abnormal features faces (wide-set eyes, low bridge of the nose, low-set ears, small jaw, no / small eye and cleft lip and palate). The third and fourth fingers, as well as the second and third toes, may be joined, and the hands may have unusual ape-like folds. There may also be defects liver and gallbladder, twisted intestines, and deformities of the fingers and toes. The placenta in triploidy can be immature, large and filled with cysts. Mosaic patients will live longer than patients with complete triploidy, but usually have mental retardation, developmental delay, depression, epilepsy, short stature, obesity and other deviations.

A pregnant mother carrying a triploid fetus sometimes experiences an increase in blood pressure (arterial hypertension), edema and the excretion of albumin in the urine (albuminuria). This condition is called toxemia or preeclampsia.

Causes

Triploidy is the presence of a complete complementary set of chromosomes. The tripling of chromosomes is caused by the fertilization of an egg with two sperm, or the fertilization of an egg by a sperm with an additional set of chromosomes, or fertilization of an egg with an additional set of chromosomes, normal sperm. This disease is not inherited and is not related to the age of the mother or father.

Affected populations

Triploidy accounts for 1-3 percent of all pregnancies. 2/3 of triploid pregnancies are in men.

Related disorders

Symptoms of the following diseases are caused by duplication, triple duplication or deletion of chromosomes:

• Tetraploidy - a condition in which one cell contains four sets of chromosomes instead of the usual two sets. The total number of chromosomes per cell in tetraploidy is 92 instead of 46. Affected babies usually miscarry early in pregnancy or die in the first days of life. Affected children have been reported to have multiple birth defects such as abnormal facial features (small head and jaw, cleft lips and palate, small eyes or eyeballs missing, ear abnormalities), heart defects, brain defects, genital anomalies and clubfoot. Tetraploidy during pregnancy can be suspected if congenital defects are detected on an ultrasound scan. A definitive diagnosis can be made by cytogenetic analysis of cells taken during pregnancy using amniocentesis or chorionic villus sampling (CVS).
• Trisomies, such as trisomy 21 (Down syndrome), are characterized by a triple chromosome. The most common symptom of trisomy is mental retardation. Chromosomes are found in the nuclei of all cells in the body. They carry the genetic characteristics of every person. Pairs of human chromosomes are numbered 1 through 22, with an unequal 23rd pair of X and Y chromosomes for males and two X chromosomes for females. In people with trisomy, an extra chromosome is added to one of the normal pairs. Triple duplication of a chromosome can be partial, or a very short arm (p +), or a very long arm (q +). Conditions are classified by the name of the abnormal pair of chromosomes and by which part of the chromosome is affected.
• Down Syndrome (trisomy 21) is the most common and easily identifiable genetic disorder caused by a chromosomal abnormality. One extra chromosome is present. Children with Down syndrome have some degree of mental retardation, which can range from mild to severe. However, most children with Down syndrome function in a mild to moderate range.
• Chromosomal 11q syndrome (Jacobsen syndrome) is a rare genetic disorder caused by the absence of the long arm of chromosome 11. The disorder may be characterized by a narrow, protruding forehead, eye problems, an abnormal shape of the nose and mouth, and mental retardation. The severity and type of the abnormality depends on the size and location of the missing chromosome. The cause of the chromosome rupture itself is unknown.
• Chromosomal 18p syndrome Is a deletion of the short arm (p) of chromosome 18. It is characterized by unusual facial features and mild to severe mental retardation. This syndrome can also include lack of growth, decreased muscle tension, and the brain is smaller than normal. There may also be behavioral problems and speech delays.

Diagnostics

The presence of several major malformations, low amniotic fluid levels, and / or growth restriction on ultrasound of the fetus during pregnancy raises suspicion of triploidy. Diagnosis can be made during pregnancy by chromosomal analysis (karyotyping) of cells obtained by amniocentesis or chorionic villus sampling (CVS). The diagnosis can be confirmed after birth by chromosome analysis of tissue (skin) obtained from the affected baby. Triploidy cannot be diagnosed using a microarray of chromosomes. The accuracy of non-invasive prenatal testing using fetal extracellular DNA (cff) for the diagnosis of triploidy is still under study. Abnormal levels of certain maternal blood proteins, such as alpha-fetoprotein, human chorionic human gonadotropin, estriol, and pregnancy-induced plasma protein-A have been associated with an increased risk triploidy.

Standard treatments

Triploidy cannot be treated or cured. Pregnancies that last before the baby is born are rare. If the infant survives, palliative care is usually provided. Medical and surgical methods of treatment are not used due to the fatal outcome of the disease.

If doctors detect triploidy during a woman's pregnancy, she can terminate the pregnancy or carry it out before the term or before a spontaneous miscarriage. If a woman decides to carry a baby before term, she should be closely monitored for complications caused by triploidy, including:

• preeclampsia, which can be life-threatening;
• choriocarcinoma, a type of cancer rarely caused by tissue left over from a partial molar pregnancy.

Forecast

Most fetuses with triploidy do not live to be born, and those that are born die, usually within a few days. Since there is no cure for triploidy, palliative care is provided if the baby survives to birth. If triploidy is diagnosed during pregnancy, termination is often suggested as an option because of the additional risks to maternal health (preeclampsia or choriocarcinoma).

Mosaic triploidy has a better prognosis, but patients have moderate to severe cognitive impairment.

How to deal with triploidy?

Losing a baby to triploidy can be difficult, but you don't need to deal with these feelings alone. Look for support groups, online forums, or discussion groups to share your experiences. Thousands of other women have also faced a situation similar to yours and sought help and support from these groups.

Carrying a baby with triploidy does not increase the chances of a similar pregnancy again, so you can conceiving another child safely without worrying about the increased risk of having another child with triploidy. If you do decide to have another baby, continue to seek antenatal care and testing to make sure your baby is receiving the best possible care.