Trisomy 21 versus Down Syndrome
Trisomy 21 and Down Syndrome are commonly used interchangeably however, there is a difference in what they mean. Trisomy 21 refers to an extra copy of chromosome 21. This means instead of having two chromosomes that are the same, there are three. Trisomy 21 is a type of aneuploidy, there are other types of aneuploidy. Aneuploidy literally means not the normal amount of sets of chromosomes (an-not normal, eu-normal, ploidy-sets of chromosomes).
Down Syndrome, on the other hand, is the outcome of having an extra copy on chromosome 21. It is unknown why in Down Syndrome that there is the same aneuploidy present but, the expression of that aneuploidy ranges from mild to severe. There is really no explanation as to why people with Down Syndrome have some characteristics and others not.
Trisomy 21 is used more to convey that there is a difference in genetics, the actual amount of chromosomes. It is the result of a genetic test to determine what is atypical. Down Syndrome is the medical diagnosis as a result of the genetic test. This makes more sense because syndrome indicates that there are a variety of characteristics that make up the range of expression from mild to moderate to severe and what causes the range is unknown.
This being said, whether you use Trisomy 21 or Down Syndrome in everyday speech, it conveys the same meaning. Although, Down Syndrome seems to be more commonly used.
Navigating my website you may see that I do not make this distinction always. I do not make the distinction because most people use the two words interchangeably and I want information to show up in searches using both words.
The Take Home Message:
Trisomy 21 and Down Syndrome are used to describe a medical condition. That is, Trisomy 21 is more a biological term. Down Syndrome is a medical term of a biological condition that a human being has. Further, people with Down Syndrome are human being first, just like you and I.
This means that people who have Down Syndrome are not a product of their condition. For example, you would not call someone who has carpal-tunnel syndrome, “a carpal-tunnel person” or “carpel-tunnel’s person”. Likewise, it is incorrect to say “Down Syndrome person” or “Down’s person”. People with Down Syndrome are more than their medical condition. They are people and a part of society thus are worthy being treated as such.