31 for 21: Forms of Down Syndrome

The most common form of Down syndrome occurs either before or during conception, an "error" in cell division creates three copies of the 21st chromosome instead of the normal two.  Because of the third twenty-first chromosome, it is also known as Trisomy 21 (or T21 for short).  Any chromosome, or part of a chromosome, can be "triplicated" however, most of those "errors", do not allow a baby to make it to birth. Because of this, Trisomy21 is the most common genetic abnormality in live births. About 95% of people living with Down syndrome have T21. 

What many are unaware of is that there are two other forms of Down syndrome. 

1-2% of all people living with Down syndrome have a form called Mosaicism. In this type of Down syndrome the "error"in the separation of the twenty-first chromosome happens after fertilization. This causes the baby to have some cells with the typical amount of forty-six chromosomes and some cells with forty-seven; the extra being in the twenty-first chromosome. Because some cell are unaffected the child's abilities and capabilities may be greater than a child with the other two forms of Down syndrome. However, it depends on the ratio of the forty-six chromosomes to the forty-seven chromosomes.

The third form of Down syndrome is called Translocation. 3-4% of individuals who have Down syndrome have this form of it. Our Vada is one of those individuals. In this form of Down syndrome a piece of the twenty-first chromosome breaks off and reattaches itself elsewhere, usually onto the fourteenth chromosome. Translocation causes every cell to have an extra piece of the twenty-first cell. In Vada's case her extra piece practically reattached itself to its original strand. 


When a child is born with Translocation  it could mean that one of the parents is a carrier of a specific chromosomal material mater. Since I had two children prior to my marriage with Justin we knew that I was not a possibility. Parent who have the arranged chromosomal material will always produce a child who would have Down syndrome. To better prepare ourselves, my husband, Justin, had genetic testing done and after two very long weeks the test showed that he is not a carrier. Therefore the Translocation just happened and we don't mind it all. 


If you are interested the test done to determine what form of Down syndrome an individual has is called Karyotyping.

This is a copy of Vada's Karyotypes. If you look at number 21, her 21st chromosome, you can see that there is an arrow pointing to an empty spot. That's where her third, twenty-first chromosome would be if she had T21. However, that third little booger jumped to its neighbor and is actually sitting on top of what would have been the middle chromosome of the group. If you look carefully you can see that the first, twenty first has only one "dot" and the second has two. That second "dot" is actually Vada's piece or her third, twenty-first. Understand? I tried not to be confusing... When I first looked at these results I thought the arrow meant that since the piece wasn't there that they were saying she didn't have Down syndrome. Low and behold, she just has another form.

The truth is, regardless of what form of Down syndrome Vada may or may not have, her diagnosis is not a negative thing to our family. Vada is an important piece to our family puzzle and without her we would not be whole. She is loved, cherished, honored and respected. Like all children, she is proof of God's perfect works.