Down syndrome is a genetic deformity caused by the presence of a complete or total extra copy of chromosome 21. The additional genetic material alters the development course and causes characteristics that are commonly related to Down syndrome. Some of these traits are “low muscle tone, small stature, an upward slant to the eyes, and a single deep crease across the center of the palm” (“Down Syndrome”). Keep in mind, however, that all individuals are different and may have different degrees of these traits, or may not have these traits at all. “According to Centers for Disease Control and Prevention, approximately every 1 in 700 babies in the United States is born with Down syndrome, making it the most common chromosomal condition” (“Down Syndrome”). Children with Down syndrome are known to have some delayed development in certain aspects, mostly when it comes to learning. Intellectual and cognitive development delay, though, can be very varied, and this goes for fine motor skills as well. On average, a child with Down syndrome will start to sit at 11 months, crawl at 17 months and will finally start to walk at about 26 months or about two years old (Crosta).
The National Down Syndrome Society explains that the condition can be traced back as far as centuries ago, with the physical traits that had been previously described being alluded to in art from those times. The condition was not officially recognized until the late 19th century, when John Langdon Down published an accurate description of a person with Down syndrome in 1866. This earned him the title of “The Father of Down syndrome”. Though others had previously documented the condition, Down gets the most credit because of his accuracy. During the more recent years, advances in technology and all the progress that science has made has led to the development of more and more detailed descriptions. In 1959, French physician Jerome Lejeune showed and identified the condition as chromosomal, thought it was originally thought to have been caused by an extra original chromosome. In 2000, an international team unveiled that the actual cause of the disorder was by the partial or complete copy of chromosome 21.
Chromosome 21 is the smallest human chromosome and accounts for about 1.5 to 2.0% of the total DNA within a cell. It consists of roughly 48 million base pairs, and likely contains anywhere from 200 to 300 genes. Issues with chromosome 21 are not limited to only Down syndrome, as it is also known to cause certain cancers and other chromosomal conditions that are all similar to Down syndrome, but are not quite the same thing. (“Chromosome 21”)
The main cause of Down syndrome, as stated before, is a partial or complete copy of chromosome 21 in either some of the cells in an organism, or all of them. What causes this extra chromosome to form is still unknown to the prying eyes of science. The National Down Syndrome Society states there is a link that is seen between the chances of having a baby with Down syndrome and the age of their mother. 80% of all babies that are born with Down syndrome were born before their mothers reached the age of 35. This statistic is believed to be caused by the higher birth rates of younger women. This makes sense due to the fact that most mothers will have children before they grow too old. Older women are more likely to give birth to a child with Down syndrome (Crosta). There is no link, however, between the cause of Down syndrome and the actions of the parents before or during pregnancy. (“Down Syndrome”)
According to the National Down Syndrome Society, there are two ways of testing for Down syndrome prior to the birth of a child: screening and diagnostic. The society states that screening tests are less definitive, and more of a probability since it predicts the chance of a fetus having Down syndrome, while diagnostic tests can give an accurate, confident result. During screen tests, both a blood test and ultrasound (sonogram) are performed (“Down Syndrome”). The process involves the calculation of the number of different substances in the mother’s blood—this measurement is combined with the woman’s age when predicting the probability of the fetus having Down syndrome (“Down Syndrome”). During the ultrasound, the back of the fetus’ neck is observed between the eleventh and fourteenth week of pregnancy; the presence of liquid in the baby’s neck is a sign of higher risk for genetic disorders and birth defects (Shafi).
Amniocentesis and chorionic villus sampling (CVS) are two examples of diagnostic tests that are performed. With amniocentesis, a sample of amniotic fluid—which contains fetal cells and substances created by the baby that protect it—is taken from the uterus during the first trimester of a pregnancy (Mayo Clinic Staff). Chorionic villus sampling, meanwhile, is typically done between ten and thirteen weeks of gestation (Mayo Clinic Staff). This is essentially what its name suggests: a swatch of chorionic villi is taken from the placenta via either the cervix or abdominal wall (Mayo Clinic Staff). At birth, karyotypes are utilized to ensure that a diagnosis is completely correct, since certain physical traits that are common to babies with Down syndrome—“low muscle tone, a single deep crease across the palm of the hand, a slightly flattened facial profile and an upward slant to the eyes” (“Down Syndrome”)—can be features of those that do not actually have Down syndrome. Along with karyotypes, a test known as FISH can also be used for confirmation. Genetic counselor Kathleen Fergus explains that FISH reveals the number of chromosomes as well as what kind, but does not specify information for every single chromosome or its structure—for example, it can show that there are a certain amount of number 21 chromosomes that are present, but will not go into specifics about its shape.
Down syndrome is not something that can be placed into a single box. Similar to autism, every single case is different and needs to be handled with a unique approach. Each person is different and must not be treated like they are just another number in a statistic. As explained by the National Down Syndrome Society, there are three different types of Down syndrome: Trisomy 21, mosaicism, and translocation. Trisomy 21, also known as nondisjunction, is created by an error in cell division that causes an embryo to have three copies of the previously mentioned chromosome 21 in each cell. As this usually occurs prior to or at conception, the cells continue to develop and the extra copy of chromosome 21 will carried through the embryo as it develops. If a pair of chromosome 21 fail to separate, the error is transmitted through every cell. Trisomy 21 is the cause of about 95% cases of Down syndrome. Mosaicism, or mosaic Down syndrome, is diagnosed when a mixture of two cells—some containing the normal 46 chromosomes and some affected cells—with 47 chromosomes are present within the same organism. This is the most uncommon form of Down syndrome and only amounts to about 1% of cases. Those who do have mosaicism show less traditional signs of Down syndrome, although with the lack of information, generalizations are not possible. The third and final type of Down syndrome that has been recognized at this point in time in known as translocation. Translocation accounts for about 4% of cases. This is caused by the attachment of a partial or complete extra copy of chromosome 21 to another chromosome, usually chromosome 14.
Although Down syndrome may share its similarities to autism, it is specifically a genetic disorder, while autism is a developmental disorder. As stated before, excess chromosomes result in impacts on development, physical features, and intellect of those diagnosed with Down syndrome. Autism, on the other hand, is said to not have a single cause, but rather, is influenced by particular environmental factors or abnormalities in the brain (autism-society.org). It is, however, possible for a person to be diagnosed with both Down syndrome and autism, and this is known as Down syndrome and autistic spectrum disorder (DS-ASD). In this case, symptoms of both disorders are evident, and there are two groups for signs/symptoms. In group one, these symptoms typically occur around infancy, such as refusing to eat food; constant, repetitive moments (ex: hand waving, fingers in mouth); having a fascination with lights, ceiling fans, or fingers. In group two, these signs are evident in older children who may show major decline in the development of language and social skills as well as have high amounts of repetitive behavior. (Capone)
Down syndrome does not discriminate—its’ cold and uncaring hands take hold on the lives of people from all different kinds of races and those from all economic statuses. So no matter skin color, nationality, or amount of wealth, the chances don’t change. They are the same for every member of the human population. A commonly asked question about Down syndrome, though, is if it is hereditary. Can it be passed down from parent to child through the means of genes? The simple answer to this question is that only 1% of Down syndrome cases are indeed hereditary. The genetic makeup of the parents have no effect on whether their child will or will not have trisomy 21. One-third of cases of translocation have a hereditary component to them which totals out to about 1% of all cases. Most of these occurrences are also sporadic or chance events. About one-third of cases have a parent as a carrier. Once a woman has a child with trisomy 21, she has a 1/100 chance of having a child with Down syndrome until she turns 40 years old. Within the father, the risk of recurrence is about 3%, and if the mother is the carrier, the risk is about 10-15%. The likelihood of birthing a child with Down syndrome also goes up with the age of the mother. Women of 35 have a 1/350 chance, at the age of 40, woman have a 1/100 chance, and at 45, that chance is 1/30. (“Down Syndrome”)
Despite hindrances in the cognition of those affected by Down syndrome (which can be from mild to severe) many who are diagnosed are still able to actively participate in various parts of the community, including school environments, work, and social activities (Down Syndrome). The National Down Syndrome Society states that this is thanks to antibiotics and clinical treatment, which have dramatically increased the lifespan of those with Down syndrome. The society also says that in 1910, most who were diagnosed only lived up to the age of nine, but today, many are reaching sixty years. Recently the amount of interaction with those with Down syndrome has increased awareness about the disorder as well. October is marked as National Down Syndrome Awareness month, and many events of celebration occur during this time, such as various restaurant fundraisers and talent shows where performances are done by those with Down syndrome (dsagsl.org).
As those with Down syndrome go through various transitions in life, their families have to ensure that they provide them with the assistance they need. It is common for individuals with Down syndrome to struggle with issues such as depression or hypothyroidism on top of their developmental and intellectual delays (nichd.nih.gov). The NIH also states that many who are in their pre-teens or teens may experience decline in school performance or go through mood changes, and so it is crucial for them to receive as much help as possible to ensure that they are successful. Individuals with Down syndrome should also be informed of subjects such as puberty, sexuality, and sexual activity since they experience changes in hormones just like everyone else (nichd.nih.gov). Parents must take a number of factors into consideration before making any major decisions (such as considering whether their child is ready to enter the job field) and need to bear in mind their child’s self-esteem, whether they can carry out tasks on their own, and if they are able to be emotionally split from family (nichd.nih.gov). As they move toward adulthood, they will acquire skills that allow them to form close relationships and live better and longer lives.
Although Down syndrome is an incurable condition that may bring issues for families with children diagnosed with the disorder, it is something that can helped by consistent treatment. Thanks to improving technology, more awareness, and specialized intervention programs that cater to an individual’s needs, those diagnosed with Down syndrome are still able to live a long and full life just like any other person.