A client is seeking information about the different types of Down syndrome.
The client asks, “What is the most common type of Down syndrome?” How should the nurse respond?
A “The most common type is trisomy 20.”..
B “Translocation Down syndrome is the most common type.”..
C “The primary type is mosaic Down syndrome.”..
D “Trisomy 21 is the most common type.”..
The Correct answer and Explanation is:
The correct answer is:
D) “Trisomy 21 is the most common type.”
Explanation:
Down syndrome, also known as trisomy 21, is a genetic disorder caused by an extra copy of chromosome 21. There are three types of Down syndrome: trisomy 21, translocation Down syndrome, and mosaic Down syndrome. Of these, trisomy 21 is the most common, accounting for about 95% of cases.
- Trisomy 21 (Nondisjunction):
This type occurs due to an error in cell division called nondisjunction. Normally, during the formation of egg and sperm cells, chromosomes are divided equally, with 23 chromosomes in each. In trisomy 21, a pair of chromosome 21 fails to separate properly during this process. As a result, the individual inherits three copies of chromosome 21, leading to the characteristic features of Down syndrome. Trisomy 21 can happen in both maternal and paternal reproductive cells, although it’s more commonly associated with older maternal age. - Translocation Down Syndrome:
In translocation Down syndrome, which accounts for about 3-4% of cases, an extra part or whole chromosome 21 is attached to another chromosome, usually chromosome 14. This type can sometimes be inherited, which differentiates it from trisomy 21, where inheritance is typically not a factor. - Mosaic Down Syndrome:
Mosaic Down syndrome is the rarest form, occurring in about 1-2% of individuals with Down syndrome. In this case, some cells have the typical two copies of chromosome 21, while others have three copies. This mosaic pattern of cell development can result in milder characteristics of Down syndrome.
The most important point to convey to the client is that trisomy 21 is the most common form of Down syndrome. This type leads to typical symptoms, including intellectual disability, distinct facial features, and other health challenges associated with the condition.