What is Down syndrome?


The following article was written by Stephanie Mamayson for the Canadian Down syndrome Society.  It is a short and concise article which accurately describes what Down syndrome is.

Down syndrome, redefined

Down syndrome is a naturally occurring chromosomal arrangement that has always been a part of the human condition. The occurrence of Down syndrome is universal across racial and gender lines, and it is present in approximately one in 800 births in Canada.

Down syndrome is not a disease, disorder, defect or medical condition. It is inappropriate and offensive to refer to people with Down syndrome as "afflicted with" or "suffering from" it. Down syndrome itself does not require either treatment or prevention.

The sole characteristic shared by all persons with Down syndrome is the presence of extra genetic material associated with the 21st chromosome. The effects of that extra genetic material vary greatly from individual to individual. Persons with Down syndrome karyotypes may be predisposed to certain illnesses and medical conditions, but that genetic arrangement does not guarantee their development. The same illnesses and conditions are also present in the general population. Timely and accurate diagnosis and appropriate treatment of these illnesses and conditions improves both the length and quality of life, to the same extent as would be expected in the population without Down syndrome. Vigilance on the part of health care practitioners is required to identify and treat any of them if they arise.

Conversely, studies have shown that people with Down syndrome have a statistically lower risk of developing certain other illnesses and medical conditions. That genetic arrangement does not guarantee that they will not develop.

Down syndrome commonly results in an effect on learning style, although the differences are highly variable and individualistic, just as in the physical characteristics or health concerns. The most significant challenge is to find the most effective, productive methods of teaching each individual. The identification of the best methods of teaching each particular child ideally begins soon after birth, through early intervention programs.

Position Statement on Redefining Down Syndrome
Approved November 2003


A Parent's Perspective - written by Sandi


It is important for me as a parent of a child who has Down syndrome to add my own information.

When asked the question, "What is Down syndrome?" there are many things that I explain.  First who discovered it?  Though it seems that in 1866 an English doctor named John Langdon Down first described the condition which subsequently took his name, the actual connection was really and more accurately discovered a lot later, in 1959.   A Professor Jerome Lejeune who was a geneticist in Paris, in 1959 made his own scientific discovery that Down Syndrome actually occurred as a result of a set (trisomy) instead of a pairing of chromosome 21.

Down syndrome, or Ds (as many families now refer to it) for short, is an "abnormal" genetic chromosomal arrangement.  It is often called a genetic abnormality, or chromosomal abnormality.  The reason is because, in a typically developing fetus (at conception) each parent provides the fetus with 23 of their own chromosomes.  The total combination of the pairing of these chromosomes normally adds up to 46.  In people who have Down syndrome, for some reason - (where this reason is still under much debate) when both parents combine the 21st chromosome, (usually resulting in a pair) one parent gives both of their copies of the 21st chromosome instead of only one.  The end result at conception is a set (three or trisomy) of the 21st chromosome, instead of the normal pair and consequently all the "issues" that result from the arrangement.  It is important to note that nothing that either parent did before pregnancy, during conception or while pregnant caused Down syndrome to occur.  While the extra copy of the chromosome can come from either the mother or father, and there is no way to know if either parent will or can provide this extra copy of the chromosome, there seems to be a definite link to occurrence with respect to the mothers age which is also not at all clear scientifically, yet.  Down syndrome is known to occur in approximately 1 in every 800 births.  And it does not discriminate meaning, anyone from any race, religion, nationality, gender, and or social-economical class can be born with Down syndrome.  It is one of those genetic conditions that is "compatible with life" meaning the syndrome itself is not fatal.  This is because it is believed that since the 21st chromosome is the smallest of all the chromosomes in the human make up, when something such as a trisomy occurs, the ability to survive is therefore not affected in the same way that some other chromosomal abnormalities do.  There are some trisomy's which are considered "not really compatible with life", such as Trisomy 13 and 18 (Patau syndrome & Edwards syndrome).  There is some evidence that indicates that of the babies that are not born that were subsequently diagnosed with or had having Down syndrome at conception, 75% did not survive past conception or fetal stages.  Of the entire percentage conceived, it seems that only 25% are actually born.  So there seems to be a high rate of loss, however because often times the fetus is or was not diagnosed these numbers tend to be unknown and also as a reuslt may therefore be inaccurate.

It is interesting to also note, the statistics show that 80% of women who have babies with Down syndrome are under the age of 30, but we know statisisticall the risk for Ds increases with maternal age.  So, if you are 20 years of age, your risk would be approximately 1:1400, and if you are 35 the risk is 1:385.  As you can see the upward trend in risk increases with maternal age, and scientists believe it is because the instructions for the arrangement of the chromosomes become more "cloudy" as we age, and for some reason the division of the pair of chromosomes (from each parent) is not instructed properly, and so the mother or father passes on the whole copy of their pair instead of only one of the 21st chromosome.  Therefore, the baby ends up with the extra copy resulting in a set or triplicate - as opposed to the regular pair.  The result is Trisomy 21 or Down syndrome.

One of the "issues" that result from Down syndrome are, certain features.  Remember though, just as everyone in the whole world is unique, so are the individuals who have Ds.  These features tend to be common in people who have Ds, but not all people who have Ds will have all the same features or characteristics.  Some of these features include, upward slanting eyes (resembling the Asian look), shorter stature, shorter limbs, shorter length fingers and toes, smaller or lower set ears, low muscle tone, smaller mouths (which tend to make their tongue appear larger or to protrude).  More information on features and characteristics can be found in more detail in my article called, "Markers, Features & Characteristics" listed on the Down syndrome menu.

In terms of the mental aspect of development for children with Down syndrome, there seems to be a lot of information that points to the fact that most (but not all) people who have Down syndrome can have mild to moderate cognitive or intellectual delays, and few that have severe ones.  However it seems that in research, if a fetus in utero has a conditional called Ventriculomagly (a brain condition that occurs when the lateral ventricles become dilated) which can be a normal or commonly occuring situation in fetues with Down syndrome and/or other genetic conditions - when those ventricles reach a moderate to severe measurement (between 10 and 15 mm, where the ventriculomegaly may be described as mild to moderate. When the measurement is greater than 15mm, the ventriculomegaly may be classified as more severe) there seems to be a correlation with the increase in delay with respect to cognitive development.  It should also be noted though, in many cases of mild ventriculomegaly, however, there is resolution of ventriculomegaly during the pregnancy.  It is very important to realize that despite this occurrence, there is proven data that shows the more care, love and early intervention given to babies and children in their developmental years, increases the ability for those same babies and children to learn and develop at typical levels and achieve the similar if not the same results as those who are not affected by delays.  Other developmental delays such as crawling, walking or talking are often attributed to a condition called hypotonia (low muscle tone) which affects the child's ability to use their muscles and strength in the same manner as a typical genetically arranged child would.  Imagine having to wear an extra 10 pounds on each limb, and be expected to match the development or movement as someone without.  It would definitely take that body longer to reach the required strength to move in a way that would otherwise be easier to achieve without the problem.  So, therapies designed to assist children with hypotonia are available such as physiotherapy, occupational therapy and osteopathy.  When delays with speech are discovered, a speech therapists should be consulted.  It is at that point (or even before by having hearing evaluated early) that the child's hearing should be checked.  Often problems associated with hearing can affect speech, and if discovered early, can be targeted and subsequently worked on so that the speech isn't affected or limited.

In this question on "What is Down syndrome", I feel it is important to address something that is very important to people who have Down syndrome. Often when we research information about medical issues, we forget about the "real" aspect of the person involved with the medical concern.  Most mediums that provide this information do not address the personal aspect of the literature.  I want to add a piece of information which I feel is extremely important and is important to families who have someone with Down syndrome in their family.  This information is "How to talk about Down syndrome."

For this topic, please click here or choose "How to talk about Down syndrome" from the WHAT IS DOWN SYNDROME menu in the "Main" menu.