Trisomy 18 (Edwards Syndrome)
Trisomy 18 also known as Edwards Syndrome is genetic disorder. This severe condition of Trisomy 18 is caused by the presence of extra copy of chromosome 18 present in the cell attached to original pair.
Introduction
Trisomy 18 is a genetic disorder which is also known as Edwards Syndrome. It is relatively common syndrome compared to Patau syndrome. Its occurrence probability ratio is 1:3000. As John H Edward first recorded its details in 1960, this genetic disorder was named after his name as ‘Edwards Syndrome’. The occurrence percentage is more in girls than boys which is about 3 times higher.
Physiology and Pathology
There are 23 pairs of chromosomes present in any cell of human body. During reproduction a normal cell of sperm or ova carry 23 individual chromosomes; one of each contributes to make 23 pairs of chromosomes. Thus, a cell of healthy fertilized egg carries 23 pairs or 46 in nos. chromosomes. In trisomy, due to some genetic disorder numerical errors occur at the time of two meiotic cell division stage which results in to failure of segregation of chromosomes into the newly formed cell. This process is known as non-disjunction which gives rise to abnormality in chromosome numbers.
In trisomy, there is an extra copy of chromosome attached to the normal pair of chromosome, making the haploid number of 24 instead of 23. Fertilization of such eggs results in trisomy. Trisomy means three copies or three numbers of a chromosome instead of two. In trisomy 18 this additional chromosome gets attached with the chromosome 18 resulting in abnormality.
Like down syndrome trisomy 18 (Edwards Syndrome) affects all organs and systems of body. It is characterized by distinct impaired facial features. Edwards Syndrome can affect individuals from all ethnic backgrounds. About 95% cases get aborted in embryonic or fetus stages and before birth, one can just predict the probability of occurrence.
The abnormal characteristic of individuals suffering from trisomy 18 relates to the extra genetic coding present because of third chromosome. As initial single cell of egg carries this extra copy of chromosome, each and every cell of the body contains the same extra genetic coding. This results into hampering the ability to grow and develop. These abilities get prolong delayed or impaired permanently. The characteristic physical abnormalities that follow the onset of Edwards Syndrome include small or abnormally shaped head, low body weight at the time of birth, small jaws or mouth, clenched fists with overlapping fingers, heart defects.
Symptoms
Trisomy 18 adversely affects all system organs of human body. Its symptoms include –
1. On nervous system and brain- Edwards Syndrome severely affects central nervous system and brain. Mental retardation and delayed brain developments are the common found brain malfunctions. High muscle tone, physical malformation, seizures can also be found.
2. Head and face- It is characterized by distinct facial abnormalities. Microganthia, (abnormally small jaws), Microcephaly (small head), low set ears, epicanthal folds, wide set eyes, small eyes, small mouth, upturned nose, prominent back portion of head, and palpebral fissures (narrow eyelid folds ) are some of the common found symptoms.
3. Heart- 90% of the victims suffer from congenital heart defects. Ventricular septal defect, Atricular septal defect, coronary valve defect, patent ductus arteriosus are known symptoms found.
4. Bones- Clenched fists with its 2nd and 5th fingers overlapped on others, severe growth retardation, rocker bottom feet, webbing, absent radius, shorten nails are some of the symptoms visible.
5. Besides this, malfunctioning and malformations of digestive tract, reproductive systems, and urinary tract are found.
Diagnosis
Before birth MRI, Ultrasound, CT, X-ray, and genetic testing can detect the presence of trisomy 18.
Ultrasound and MRI can detect the abnormalities in the fetus. Genetic testing by means of amniocentesis can confirm the occurring of trisomy 18. CT scans and X-rays can confirm abnormalities in brain and skeleton system respectively. After birth blood test can confirm the diagnosis. Even the visible features of facial impairment or bone abnormalities can help in the diagnosis of trisomy 18.
Prognosis
As more than half of the affected infants do not survive beyond 5 to 6 days so these abnormalities are not compatible with more than 2 to 3 months. Very rare cases have survived to teen age but suffered severely with handicaps and finally succumb.
Treatment
Due to its nature, life sustaining measures are not recommended. The medical treatment for individuals suffering from trisomy 18 is always supportive which is focused on treating infections, heart problems and providing nutrition. Due to its complex, multifaceted nature only 5% chance of survival up to 1 year of age is present.
Trisomy 18 is a genetic disorder which is also known as Edwards Syndrome. It is relatively common syndrome compared to Patau syndrome. Its occurrence probability ratio is 1:3000. As John H Edward first recorded its details in 1960, this genetic disorder was named after his name as ‘Edwards Syndrome’. The occurrence percentage is more in girls than boys which is about 3 times higher.
Physiology and Pathology
There are 23 pairs of chromosomes present in any cell of human body. During reproduction a normal cell of sperm or ova carry 23 individual chromosomes; one of each contributes to make 23 pairs of chromosomes. Thus, a cell of healthy fertilized egg carries 23 pairs or 46 in nos. chromosomes. In trisomy, due to some genetic disorder numerical errors occur at the time of two meiotic cell division stage which results in to failure of segregation of chromosomes into the newly formed cell. This process is known as non-disjunction which gives rise to abnormality in chromosome numbers.
In trisomy, there is an extra copy of chromosome attached to the normal pair of chromosome, making the haploid number of 24 instead of 23. Fertilization of such eggs results in trisomy. Trisomy means three copies or three numbers of a chromosome instead of two. In trisomy 18 this additional chromosome gets attached with the chromosome 18 resulting in abnormality.
Like down syndrome trisomy 18 (Edwards Syndrome) affects all organs and systems of body. It is characterized by distinct impaired facial features. Edwards Syndrome can affect individuals from all ethnic backgrounds. About 95% cases get aborted in embryonic or fetus stages and before birth, one can just predict the probability of occurrence.
The abnormal characteristic of individuals suffering from trisomy 18 relates to the extra genetic coding present because of third chromosome. As initial single cell of egg carries this extra copy of chromosome, each and every cell of the body contains the same extra genetic coding. This results into hampering the ability to grow and develop. These abilities get prolong delayed or impaired permanently. The characteristic physical abnormalities that follow the onset of Edwards Syndrome include small or abnormally shaped head, low body weight at the time of birth, small jaws or mouth, clenched fists with overlapping fingers, heart defects.
Symptoms
Trisomy 18 adversely affects all system organs of human body. Its symptoms include –
1. On nervous system and brain- Edwards Syndrome severely affects central nervous system and brain. Mental retardation and delayed brain developments are the common found brain malfunctions. High muscle tone, physical malformation, seizures can also be found.
2. Head and face- It is characterized by distinct facial abnormalities. Microganthia, (abnormally small jaws), Microcephaly (small head), low set ears, epicanthal folds, wide set eyes, small eyes, small mouth, upturned nose, prominent back portion of head, and palpebral fissures (narrow eyelid folds ) are some of the common found symptoms.
3. Heart- 90% of the victims suffer from congenital heart defects. Ventricular septal defect, Atricular septal defect, coronary valve defect, patent ductus arteriosus are known symptoms found.
4. Bones- Clenched fists with its 2nd and 5th fingers overlapped on others, severe growth retardation, rocker bottom feet, webbing, absent radius, shorten nails are some of the symptoms visible.
5. Besides this, malfunctioning and malformations of digestive tract, reproductive systems, and urinary tract are found.
Diagnosis
Before birth MRI, Ultrasound, CT, X-ray, and genetic testing can detect the presence of trisomy 18.
Ultrasound and MRI can detect the abnormalities in the fetus. Genetic testing by means of amniocentesis can confirm the occurring of trisomy 18. CT scans and X-rays can confirm abnormalities in brain and skeleton system respectively. After birth blood test can confirm the diagnosis. Even the visible features of facial impairment or bone abnormalities can help in the diagnosis of trisomy 18.
Prognosis
As more than half of the affected infants do not survive beyond 5 to 6 days so these abnormalities are not compatible with more than 2 to 3 months. Very rare cases have survived to teen age but suffered severely with handicaps and finally succumb.
Treatment
Due to its nature, life sustaining measures are not recommended. The medical treatment for individuals suffering from trisomy 18 is always supportive which is focused on treating infections, heart problems and providing nutrition. Due to its complex, multifaceted nature only 5% chance of survival up to 1 year of age is present.
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