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Down syndrome

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Child with Down syndrome

Down syndrome, also known as trisomy 21, is a chromosomal disorder where an individual has an irregular number of chromosomes. The person will have three twenty-first chromosomes. This will cause the person to have distinct physical features and mild mental retardation. Close to 4000 children are born with Down syndrome each year. This means that one child out of every 700 to 1000 is born with Down syndrome. [1] There is no possible way to prevent Down syndrome from occurring. Although it is more common after the age of thirty-five, a woman can still become pregnant with a Down syndrome child at any age. Although Down syndrome causes many health issues, both physical and mental, people who have the disease learn to live their lives to the fullest. Many people with Down syndrome live close to normal lives by attending school, working, and spending time with their family and friends.

History

British Physician, John Langdon Haydon Down, first classified Down syndrome in 1866. [2] During much of the nineteenth century, people with mental retardation were commonly known as Idiots. Dr. Down classified people with trisomy 21 as Mongolian Idiots. This term is now considered offensive towards those with Down syndrome and is not a politically correct term. [3] Mongolism was renamed Down Syndrome after Dr. Down in the 1960’s.[4] During the early twentieth century, people with Down syndrome were often the victims of Abuse. Many were institutionalized and were forced to undergo sterilization programs. In Nazi Germany, Many people with mental retardation, primarily those with Down syndrome, were cruelly murdered. Today, much has changed in the way people with mental retardation are treated. Many are given the chance to receive an education in public school and there are an increasing number of job opportunities available to people with mental disabilities. [5]

Common Characteristics

Child with Down syndrome showing eyes exhibiting both Brushfield spots and heterochromia

Down syndrome has many common physical characteristics. The following are some of the most common characteristics: the head is smaller than average, the face is flat, and the mouth is small. The slits of the eyes are narrow and have an epicanthal fold (a skin fold of the upper eyelid), and Brushfield spots are commonly seen in the iris. The ears are small and lower set on the head, and the neck is shorter than average. The length of the arms and legs are not proportionate to the size of the body. The feet are wide and short towed. [6] Hands tend to be wide with short fingers. The hands will exhibit a single palmar crease, which is commonly know as simian creases, which are single lines that run across the hand. [7] Another common characteristic in people with Down syndrome is hypotonia. Hypotonia is low muscle tone of the body. Infants with hypotonia will appear floppy and loose in appearance, and they will have little control of their heads and limbs. If therapy is started at a young age for hypotonia, the muscles will develop more strongly.[8]

Trisomy 21

Trisomy, the hallmark of Down syndrome, results when a baby is born with three copies of chromosome 21 instead of the usual two.

Down syndrome is a disease caused by an irregular number of chromosomes. There are three causes of trisomy 21. [9]The most common is called nondisjunction. Nondisjunction happens during cell division. When a cell goes normally through meiosis, the chromosomes are divided evenly between the two daughter cells, but when no disjunction occurs, the chromosomes are split unevenly, giving one daughter cell extra chromosomes and the other one a less than normal amount. [10] If and egg or sperm cell with an uneven number of chromosomes combines with a normal cell, the resulting fetus will have a third twenty-first chromosome, and therefore, will have Down syndrome.

Robertsonian Translocation is the second leading cause of Down syndrome. Robertsonian Translocation is a condition that causes breaks to occur in the chromosomes. These breaks normally occur in the thirteenth through fifteenth and the twenty-first or twenty-second chromosomes. Individuals with this condition have a high risk of giving birth to a child with a chromosomal imbalance. A woman who has Robertsonian Translocation affecting her twenty-first chromosome has a ten to fifteen percent chance that she will give birth to a child with Down syndrome.[11]

The third cause of trisomy 21 is mosaicism. Mosaicism is a condition were an individual has cells that do not all have the same genes. Some cells have a normal number of chromosomes while others have an abnormal amount. This condition can affect a person’s sperm and egg cells as well. If a parent's reproductive cells has and abnormal amount of chromosomes, their child could be born with Down syndrome.[12]

Diagnosis

There are currently two types of tests available for women that will test for Down syndrome. The first tests are the screening tests. The screening tests estimate a women’s chance of giving birth to a Down syndrome baby, but they will not actually determine if a woman is pregnant with a Down syndrome fetus. These tests are often preformed via ultrasound. There is also a screening test that checks properties of the blood. The second tests can determine if a woman is pregnant with a Down syndrome fetus. These tests are the Diagnostic tests. There are three types of Diagnostic tests: Chorionic Villus Sampling (CVS), Amniocentesis, and Percutaneous Umbilical Blood Sampling (PUBS).[13]

Amniocentesis is preformed between the twelfth and twentieth week of the pregnancy. It tests the amniotic fluid, which surrounds the fetus.[14]

Chorionic Villus Sampling is a test preformed between the eighth and twelfth week of pregnancy. It is often preformed on woman over the age of thirty-five, because their chance of having a Down syndrome child greatly increases. This test is preformed by obtaining a biopsy of chorionic villi from the placenta[15]

The third Diagnostic test, Percutaneous Umbilical Blood Sampling, is done after twenty weeks of pregnancy. During this test, fetal blood is obtained from the umbilical cord. It is very similar to amniocentesis. It is often used when the other test have been inconclusive.[16]

Health

The Heart

Health issues often arise in people born with Down syndrome. Nearly half of all children born with Down syndrome suffer from complications with their hearts. Children born with heart problems often have their disease divided into three categories: Atrioventricular septal defects, Ventricular septal defect (VSD), atrial septal defect (ASD), or patent ductus arteriosus (PDA), and other complex heart diseases. [17]

Atrioventricular septal defect is when the heart does not fully develop. This condition occurs primarily in children with Down syndrome. Fifteen to twenty percent of all newborn Down syndrome children are born with this disease.[18] Atrioventricular septal defects occur when the endocardial cushion does not fully develop into the atrial septum, ventricular septum, or the AV valves. This will cause there to be a hole in the heart, differentiating in severity. [19]

Ventricular septal defect, atrial septal defect, and patent ductus arteriosus are all forms of congenital heart disease where holes have formed in the heart. Ventricular septal defect is when a hole forms between the two lower chambers of the heart, also known as the ventricles. Ventricular septal defect is sometime treated by heart surgery, but often that isn’t needed because it is common for the hole to close on its own. [20] Atrial septal defect is the formation of a hole between the upper chambers of the heart, the atria. Atrial septal defect is normally treated successfully with very little complications.[21]lastley, patent ductus arteriosus is a condition that occurs after the child has been born. In a normal child, the aorta and the pulmonary artery are connected by the ductus ateriosus. The ductus ateriosus closes soon after birth in a normal child, but in some cases it remains open. Patent ductus arteriosus can be treated with an operation, but sometimes the blood vessel will eventually close on its own.[22]

Other complex heart conditions that arise in children with Down syndrome involve Tetralogy of Fallot and Hypoplastic Left Heart Syndrome. Tetralogy of Fallot is a complex heart condition. It is when the heart forms a Ventricular septal defect, pulmonary stenosis (a blockage to the lungs), and the aorta lies directly over the hole in the heart. This causes oxygenated and non oxygenated blood to mix together and flow throughout the body. This disease can be successfully treated with heart surgery. [23] Hypoplastic Left Heart Syndrome is a serious condition where the heart remains underdeveloped. Blood is not properly pumped through the heart. The only treatment for this complex heart disease is a heart transplant or an operation.[24]

Vision and Hearing

Half of all children born with Down syndrome develop problems involving vision and hearing impairment. Hearing loss in children with Down syndrome is often caused by the build up of fluid in the ear canal. It can also be cause by the shape of the ear as well. Common vision impairments that evolve in children with Down syndrome include amblyopia (the strengthening of one eye, causing the other eye to become “lazy”), a high risk of cataracts, and near or farsightedness. [25]

Other

Many other health risks often develop in those who have Down syndrome. These include: acute lymphocytic leukemia (a type of blood cancer), intestinal problems, and thyroid disease. As well as having a high risk for disease, people with down syndrome have a short life expectancy of fifty-five years; although people have been reported to live past eighty. Down syndrome causes accelerated aging which leads to an early death. Also, Alzheimer’s dementia is very common in older people with Down syndrome.[26]

Abortion

Main Article: Abortion

A very common political debate is centered around Down syndrome and abortion. Abortion is the termination of a human life while it is still in the womb. The political debate that has risen up is whether it acceptable to abort a child because it has mental disabilities. Currently, almost ninety percent of Down syndrome children are aborted. It is extremely disturbing to know that so many people kill innocent children, just because they are different than the general population. Children with Down syndrome grow up to be functional adults that are capable of holding down a job and living with little assistance. [27]

God's Plan

"For I know the plans I have for you," declares the LORD, "plans to prosper you and not to harm you, plans to give you hope and a future." Jeremiah 29:11 (NIV)

God has a plan for every person he creates, and He has a purpose for creating people with mental disabilities. God loves them equally as much as he loves everyone else and intends for them to prosper and thrive. Although a person who suffers from mental retardation has many set backs in their life, they often have a great calling. People who suffer from Down syndrome often excel in life. They become role models to others, and can often be successful in their careers. [28]

Many people in the world view Down syndrome as a negative thing. Many health issues arise in people with Down syndrome but those people could not live happier lives. God has truly blessed them through their disease. People with Down syndrome are loving, honest, talented, and happy. They do not fret over the type of things we do. Over all, they live simple, joyful lives. [29]

References