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Trisomy is a general term that is used to give a description of the presence of three chromosomes instead of the usual single pair of chromosomes. Different types of trisomy develop depending on the type of chromosomes that are involved. For instance, if a child is born with three copies #21 chromosomes instead of the normal pair, the child is said to have “trisomy 21”. Trisomy is also referred to as Down syndrome (Lippincott Williams, 2009). Therefore, trisomy 13 and trisomy 18 are genetic disorders that have inclusion of a combination of defects that occur during birth, such as mental retardation and health problems that involve almost all organ systems of the body.
Trisomy 13 and trisomy 18 mean that in each cell of the body there are three copies of # chromosome 13 and chromosome 18 respectively. Trisomy 13 is also referred to as “Patau Syndrome” after the physician who named it, while trisomy 18 is also referred to as “Edwards Syndrome” in honor of the physician who described it. Researches have shown that about 10 percent of the children who are born with trisomy 13 and trisomy18 survive the first year of life. However, there are few reports showing that there are few babies with trisomy who reach teen age.
Trisomy 13 was recognized in1960 by Patau. Trisomy 13 has been attributed to heart and brain malformations. Research shows that children with trisomy 13 have long term survival than it was previously. Trisomy 18 is the second most common trisomy after trisomy 21. It is caused by a genetic abnormality that occurs before conception. Trisomy 18 was discovered by British geneticist John Hilton Edwards in 1960. Trisomy 18, which is caused by non-disjunction, cannot be passed on to future generations (Benacerraf, 2008). Babies who have been diagnosed with trisomy do not live more than 6 days. Fetuses that are identified with trisomy 18 are in most cases miscarried. Trisomy 18 occurs mostly in the 18th chromosomal pair.
Causes of Trisomy 13
Trisomy 13 is caused by the presence of three copies of genetic material from chromosome 13 rather than the normal two copies. Stevenson (2006) explains that the excess DNA from chromosome 13 is seen in some or all body’s cells. Trisomy 13 can occur in three forms: trisomy 13 mosaicism, partial trisomy and trisomy 13. Trisomy 13 mosaicism occurs when the extra chromosome 13 DNA occurs in some cells. Trisomy 13 occurs when the third chromosome occurs in all the cells, and partial trisomy occurs when a part of the extra chromosome 13 occurs in the body’s cells. This extra material usually affects the normal development of a baby.
Signs and Symptoms of Trisomy 13
There are various signs and symptoms that are associated with trisomy 13. These symptoms include: groove in the upper cleft lip, intense intellectual disability, incomplete closure of the roof of the mouth, development delays, undescended testes in boys, and presence of extra fingers and toes. There are also no complete development of some parts of the brain, such as the forebrains, structural heart diseases during birth, and kidney abnormalities. There is a small head that has a sloping forehead, skin folds that are vertical covers the eyes in the inner corners, and scalp defects and low set ears. There is retarded growth and failure to gain weight at the rate that is expected and serious difficulties in feeding, diminished muscle tone and episodes where there is a temporary cessation of extemporaneous breathing. There are complications that may develop during infancy that may be life threatening.
Treatment of Trisomy 13
Researches have done adequate, but there has been no real cure of trisomy 13. However, treatment of trisomy 13 is scheduled on the case-by-case basis. Care is normally directed towards making babies comfortable. Therefore, the type of care and treatment that is directed to the patient is largely dependent on the patient’s condition. Surgical interventions are suspended for the first few months of life due to high death rates of children diagnosed with trisomy 13. Surgical is carried out to correct heart defects and cleft lip and cleft palate. Occupational, physical, and speech therapy are carried out to help individuals to reach their normal development potential.
Prevention of Trisomy 13
Preventive measures of this syndrome can be identified before a child is born by amniocentesis with the study of chromosomes that are in amniotic cells. Moreover, it parents who have a child infected with trisomy 13 that is usually caused by translocation are advised to go for genetic testing and counseling. This helps them to avoid having a child with trisomy syndrome in imminent pregnancies
Trisomy 18 is a disorder that is genetically transmitted, where a person has three pairs of genetic material that is contained in chromosome 18 rather than the normal pair or two copies of this genetic material.
Causes of Trisomy 18
Trisomy 18 occurs when three copies of genetic material from chromosome 18 appear in a cell rather than the normal two pairs. This is due one of eggs either from the mother or from the father containing the wrong number of chromosomes. During conception, the mistake is passed on to the baby. Trisomy 18 causes abnormal development in babies. Three types of trisomy 18 exist: partial trisomy, mosaic trisomy and full trisomy. Mosaic trisomy occurs when the extra chromosome appears in some of the baby’s cells. Full trisomy is the condition, where the extra chromosome appears in all the cells in the baby’s body, while partial trisomy 18 is a condition in which the baby has some part of the extra chromosome.
Signs and Symptoms of Trisomy 18
Trisomy 18 is characterized by several signs and symptoms that are very distinct. These symptoms vary from one individual to another. There is no particular way to know the actual symptoms of trisomy 18. It is normally linked to a high death rate. Trisomy 18 can be detected before birth, where abnormal large uterus, smaller placenta than normal and extra amniotic fluids are observed in pregnant women. Trisomy 18 is associated with several defects and abnormalities, which include low birth weight, low-set ears, small head or jaw, a cleft lip and palate, mental retardation, kidney problems, hearing loss, eye defects, heart defects, and esophageal atresia. There is also a small pelvis with limited hip movement, delayed growth, underdeveloped nails, and many other developmental delays. Male children with trisomy 18 have undescended testes. Babies with trisomy 18 normally have problems in breathing, feeding and gaining weight. They have been also observed to have increased muscle tone, seizures, and clenched hands with their fingers mounted on others especially the second and fifth fingers.
For children with trisomy 18, treatment is scheduled on a case-by-case basis. The treatments that are used depend on the condition of individual patient.
This syndrome can be prevented by carrying out genetic testing for parents who are known to have a child with this syndrome. They undergo counseling on how to avoid such cases in future generations.
Trisomy 13 and trisomy 18 are fatal genetic disorders that need people enlightened, so that they can take precaution measures when engaging into relationships. This will help reduce such incidences in future generations.