About Down syndrome


As many of you know, our oldest son, Joey has Down syndrome and Autism. We found out when I was 18 weeks pregnant that we were going to be blessed with a chromosomally enhanced child via CVS due to markers found during one of my routine ultrasounds.

I had several people say to me in the past say to me, "you knew while you were pregnant and didn't do anything about it?". It made (still makes) my blood boil when this was said to me. I NEVER at any point considered abortion with him. Once I was told there was a 50% chance that my baby was going to have Down syndrome, I needed to know so I could better prepare myself for having a child with Down syndrome, it was a serene acceptance of my child.

You can read my prenatal story on Be Not Afraid's website.


“Never tire of firmly speaking out in defense of life from its conception and do not be deterred from the commitment to defend the dignity of every human person with courageous determination. Christ is with you: be not afraid!” Pope John Paul II


Karyotype of a male with Down syndrome

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A few of my posts on Down syndrome:
Dr. Jérôme Lejeune: future saint? 
 What do all of these famous people have in common??

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The following is courtesy of the National Down Syndrome Society:

What is Down syndrome: 


In every cell in the human body there is a nucleus, where genetic material is stored in genes.  Genes carry the codes responsible for all of our inherited traits and are grouped along rod-like structures called chromosomes.  Typically, the nucleus of each cell contains 23 pairs of chromosomes, half of which are inherited from each parent. Down syndrome occurs when an individual has a full or partial extra copy of chromosome 21.
This additional genetic material alters the course of development and causes the characteristics associated with Down syndrome. A few of the common physical traits of Down syndrome are low muscle tone, small stature, an upward slant to the eyes, and a single deep crease across the center of the palm - although each person with Down syndrome is a unique individual and may possess these characteristics to different degrees, or not at all.


How common is Down syndrome?
One in every 691 babies in the the United States is born with Down syndrome, making Down syndrome the most common genetic condition. Approximately 400,000 Americans have Down syndrome and about 6,000 babies with Down syndrome are born in the United States each year. 

When was Down syndrome discovered?

For centuries, people with Down syndrome have been alluded to in art, literature and science. It wasn’t until the late nineteenth century, however, that John Langdon Down, an English physician, published an accurate description of a person with Down syndrome. It was this scholarly work, published in 1866, that earned Down the recognition as the “father” of the syndrome. Although other people had previously recognized the characteristics of the syndrome, it was Down who described the condition as a distinct and separate entity.


In recent history, advances in medicine and science have enabled researchers to investigate the characteristics of people with Down syndrome. In 1959, the French physician Jérôme Lejeune identified Down syndrome as a chromosomal condition. Instead of the usual 46 chromosomes present in each cell, Lejeune observed 47 in the cells of individuals with Down syndrome. It was later determined that an extra partial or whole copy of chromosome 21 results in the characteristics associated with Down syndrome. In the year 2000, an international team of scientists successfully identified and catalogued each of the approximately 329 genes on chromosome 21. This accomplishment opened the door to great advances in Down syndrome research.

Are there different types of Down syndrome?
There are three types of Down syndrome:  trisomy 21 (nondisjunction), translocation and mosaicism.

(Trisomy 21) Nondisjunction

Down syndrome is usually caused by an error in cell division called "nondisjunction."  Nondisjunction results in an embryo with three copies of chromosome 21 instead of the usual two.  Prior to or at conception, a pair of 21st chromosomes in either the sperm or the egg fails to separate.  As the embryo develops, the extra chromosome is replicated in every cell of the body.  This type of Down syndrome, which accounts for 95% of cases, is called trisomy 21. 

Mosiacism
Mosaicism occurs when nondisjunction of chromosome 21 takes place in one - but not all - of the initial cell divisions after fertilization.  When this occurs, there is a mixture of two types of cells, some containing the usual 46 chromosomes and others containing 47.  Those cells with 47 chromosomes contain an extra chromosome 21. 
Mosaicism accounts for about 1% of all cases of Down syndrome.  Research has indicated that individuals with mosaic Down syndrome may have fewer characteristics of Down syndrome than those with other types of Down syndrome.  However, broad generalizations are not possible due to the wide range of abilities people with Down syndrome possess. 
Translocation 
Translocation accounts for about 4% of all cases of Down syndrome.  In translocation, part of chromosome 21 breaks off during cell division and attaches to another chromosome, typically chromosome 14.  While the total number of chromosomes in the cells remain 46, the presence of an extra part of chromosome 21 causes the characteristics of Down syndrome. 
What is the likelihood of having a child with Down syndrome? 
Down syndrome occurs in people of all races and economic levels, though older women have an increased chance of having a child with Down syndrome. A 35 year old woman has about a one in 350 chance of conceiving a child with Down syndrome, and this chance increases gradually to 1 in 100 by age 40. At age 45 the incidence becomes approximately 1 in 30. The age of the mother does not seem to be linked to the risk of translocation.  

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