Causes of Down Syndrome
Opportunities for Development
Approaches to Treatment
Integration into Society
B as an Example
In this paper I will reference a total of three books, a newspaper article, and several conversations with B and his parents. I have chosen the topic of opportunities for development as the focus of my work, because it seems the most important. This paper is a short survey of Down syndrome and will only briefly examine the various aspects thereof.
The remarks about B should illustrate that people with Down syndrome also are capable of achievement in their lives. This should be self-evident and normal, but unfortunately in our society today it remains somewhat unique and of an anomaly.
Causes of Down Syndrome
The phenomenon of Down syndrome was first described by John Langdon Haydon Down in his piece “Observation on an ethnic classification of idiots” (Dittmann, 1992, p. 9). Down described these people as having a “mongolian type of idiocy” (Dittmann, 1992, p.9) and provided a detailed description of them. He described their appreciation of humor and gestures, their limited language ability, and a certain intelligence – “the apprentice [can] easily be made useful” (Dittmann, 1992, p.9).
The causes of Down syndrome were long puzzled over and this led to much argument. Thus at the beginning of the 20th century there spread a series of misguided explanations. Some physicians were of the opinion that the disability arose from “environmental factors […], alcoholism, syphilis, and tuberculosis” (Pueschel, 1995, p. 38). Some proposed tenuous speculation that Down syndrome was a “de-evolution towards a primitive early human” (Pueschel, 1995, p. 38).
At the beginning of the 20th century, people with Down syndrome were mostly classified as being “on the lowest level of the five racial developmental stages as formulated by Blumenbach” (Pueschel, 1995, p. 10). Crookshank was the first to advance this classification system in 1924, when he characterized people with Down syndrome “as a regression to a “non-human species”, “like an orangutan” (Pueschel, 1995, p.10). This debasement of people with Down syndrome was the basis of the campaign for their annihilation during the Third Reich.
It was not until the 1930s that a chromosomal mutation was hypothesized to be the cause for Down syndrome. In 1956 researchers were finally able to view chromosomes and just three years later Jérôme Lejeune in Paris was able to verify that there was a small additional chromosome in the cells of children with Down syndrome. With further experiments it was discovered that there were three of chromosome 21 present in all of these cells. Thus we arrive at the current name, trisomy 21.
In the last thirty years new hypotheses emerged that tried to account for the cause of Down syndrome. Causes such as “radiation, drug usage, hormone and immunosuppressants, spermicidal agents, and certain viral infections” (Pueschel, 1995, p. 46) were named, but despite the theoretical possibility of such causes, there is no evidence for these hypotheses.
Today there is the trend to integrate people with Down syndrome into society, to support each of them individually, and to offer them the best possible developmental opportunities. But unfortunately we feel the effects of the ignorance of certain scientists when descriptors like “monkey foot, webbing formation, buffalo hump” (Pueschel, 1995, p.10) are used for certain physical characteristics.
Down syndrome is caused when there is a defect in cell division, resulting in the presence of 47 chromosomes instead of 46. This error in cell division – sometimes called “non-disjunction” - can occur in three different places: in sperm (20-30%), in eggs (70-80%), or in germ cells (only very rarely). The mechanism of non-disjunction, no matter the type of cell it occurs in, is the same. In the course of cell division, the two chromosomes fail to separate normally from each other and instead stay joined. This results in the extra 47th chromosome.
Only rarely does it happen that one of both parents is a carrier for this disability. This type of transmission is also known as “balanced-carrier” or “translocation-carrier” transmission. This parent is phenotypically normal and has the same number of genes. However, two chromosomes are “stuck” to one another, so that each cell has a total of 45 chromosomes. The additional chromosome is often joined to another chromosome, usually with chromosomes 14, 21, or 22. It need not be the entire chromosome that is “stuck on”; it is enough when just part of it is. These parents have a higher risk of having a child with Down syndrome.
About 95% of all children with Down syndrome have a form of free trisomy 21. This non-disjunction occurs either in sperm cells, egg cells, or in germ cells. If the parents already have a child with Down syndrome and they are not translocation carriers, then they have a 1% risk of having a subsequent child with Down syndrome.
The third form of chromosomal dysfunction is referred to as “mosaic” trisomy. This form occurs in only about 1% of cases. Here, the error occurs in the first stage of cell division. In this form of Down syndrome, according to Pueschel, the symptoms are not so pronounced and there is a better mental capacity.
In the last few years, researchers have found that it is not the entirety of chromosome 21 that is responsible for the onset of Down syndrome, but just a small part of the long arm of the chromosome. The exact areas that are responsible for the onset of the disability have not yet been located.
A certain connection between the age of the mother (as well as that of the father) and the appearance of Down syndrome has been identified. At age 35, a woman’s chances of having a child with Down syndrome increase substantially. A 35 year old woman has an increased likelihood of 1:200 – 300 of having a child with Down syndrome. From age 35 and on, the risk doubles every 2 ½ years. For fathers, the risk increases at ages 45 or 50, but only slightly.
In the last few decades, genetic counseling has significantly improved. However, each case needs to be considered on an individual basis to determine if a prenatal examination is a wise choice or if it could be harmful to the unborn child. If at all possible, only groups at risk should be examined, since the risk of miscarriage is present.
There are many different examination possibilities for a prenatal diagnosis. Here I will address the three that I consider important.
Amniocentesis (amniotic fluid examination) was a method adopted in the 1970s. At an ultrasound checkup between the 14th and 16th weeks of pregnancy, a needle is inserted into the amniotic sac and 15-20 ml of fluids are extracted. These fluids are put into a centrifuge; the obtained cells are multiplied and processed in an analysis of chromosomes. The disadvantage of this method is its relatively late application.
Some physicians believe they can detect the presence of Down syndrome during an ultrasound. Supposedly, thick skin on the throat or the length of the leg bones is a sign of Down syndrome. The successfulness of this method is, however, questionable.
A further – but still controversial – position is that chromosomal mutations, including Down syndrome, can be detected by low levels of alpha-fetoprotein (AFP). A universally accepted guideline for appropriate levels of AFP has not yet been determined.