Triploid Syndrome is an extremely rare chromosomal disorder. Individuals with triploid syndrome have three of every chromosome for a total of sixty-nine rather than the normal forty-six chromosomes. Babies with Triploid Syndrome usually are lost through early miscarriage. However, some infants have been born and survived as long as five months. Affected infants are usually small and have multiple birth defects. Those that survive are usually mosaic, meaning that some cells have the normal number of 46 chromosomes and some cells have a complete extra set of chromosomes.
Triploid Syndrome may include larger than normal size placenta, lack of prenatal skeletal growth, widely spaced eyes (ocular hypertelorism), low nasal bridge, low-set malformed ears and a smaller than normal sized jaw. The third and fourth fingers of the hands may be connected and the hands may have unusual simian creases. The infant may have congenital heart defects and genital abnormalities may be present in males. There may be abnormal brain development, lack of development of the adrenal glands and cystic kidneys. Growth of the brain or spinal cord outside of the body (neural tube defects), openings in the abdominal wall, an unusually shaped skull and cleft lip and/or palate have also been observed. There may also be liver and gallbladder deformities, twisted colon and finger and toe deformities. Individuals who are mosaic will survive longer than those with complete triploidy but usually have mental retardation.
The pregnant mother carrying a triploid fetus sometimes experiences extremes of high blood pressure (hypertension), swelling (edema), and excretion of albumin in the urine (albuminuria). This condition is called toxemia or preeclampsia. Triploidy is frequently diagnosed in pregnancies in which there is a cystic placenta (partial mole). The Triploid Syndrome has been associated with pregnancies that occur soon after oral contraceptives are discontinued or after long menstrual cycles. Triploidy has been reported in conceptions that occurred following in vitro fertilization and in conceptions after a history of repeated miscarriages.
Triploid Syndrome is caused by a complete extra set of chromosomes. The triplication of the chromosomes is most often caused by fertilization of an egg by two sperm. Triploidy can also be caused by fertilization of an egg by a sperm that has an extra set of chromosomes or fertilization of an egg that has an extra set of chromosomes by a normal sperm. This disorder does not run in families and is not associated with maternal or paternal age.
Triploid syndrome can be diagnosed thorough cytogenetic (chromosome) analysis on a blood specimen. It can be diagnosed prenatally through cytogenetic analysis of cells obtained through amniocentesis or chorionic villus sampling. Abnormal levels of specific maternal blood proteins such as alpha-fetoprotein, human chorionic gonadotropin, estriol and pregnancy-assisted plasma protein-A have been associated with an increased risk for triploidy.
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