Down Syndrome

Down syndrome (DS or DNS) or Down's syndrome, also known as trisomy 21, is defined as a genetic disorder caused by the presence of all or part of a third copy of chromosome 21. It is typically associated with physical growth delays, characteristic facial features, and mild to moderate intellectual disability. The average IQ of a young adult with Down syndrome is 50, equivalent to the mental age of an 8 or 9 year-old child, but this varies widely.

What is Down Syndrome?

Down syndrome is a genetic disorder that results in varying degrees of physical and mental retardation. The condition varies in severity, causing developmental problems that range from mild to severe. The disorder occurs as a result of extra genetic material.

In most people, the genes are contained on 23 pairs of chromosomes, for a total of 46 chromosomes. Most people with Down syndrome have an extra copy of the 21 chromosome, for a total of 47 chromosomes.

Down syndrome is the most common chromosomal disorder. An estimated 1 in 800 infants are born with Down syndrome. Down syndrome is also a common cause of miscarriage. Every year, as many as 5,000 babies are born with Down syndrome in the United States.

Every year, one child in every 800 to 1,000 births will be born with a condition known as Down syndrome. Down syndrome is a disorder in which the child has extra genetic material. This extra genetic material causes the baby to develop differently in the womb. This abnormal development occurs during the early stages of cell division, soon after conception.

There is no known reason for Down syndrome or a cure for it.

The disorder came by its name when an English physician, John Langdon Down, published a description of the characteristics of a person with the condition in 1886. Since Dr. Down was the first person to give the syndrome a name, the disorder is known as Down syndrome.

There are three distinct forms of Down syndrome.

1. The most common form is Trisomy 21. This is when a child has an extra chromosome 21.

Instead of having 46 chromosomes in each cell (23 from the father and 23 from the mother), he has 47. Ninety-five percent of children born with Down syndrome have Trisomy 21.

2. Translocation is another form of Down syndrome and makes up 3 to 4 % of the population of people with the disorder. Translocation occurs when part of chromosome 21 breaks off and attaches to another chromosome, changing the genetic makeup. In this form of Down syndrome, each cell has the normal 46 chromosomes, but there is extra genetic material from the broken off chromosome.

3. The third and final form is called Mosaicism, and is the rarest form of Down syndrome, occurring in only 2 % of all cases. Mosaicism happens when some of the cells in the forming embryo have 46 chromosomes, and some have 47. Thus, the alternating pattern gives it the name Mosaicism. People with Mosaicism may not be as affected with the physical and/or developmentally delayed characteristics of those born with the other two forms of Down syndrome.

Babies with Down syndrome are usually diagnosed at birth or shortly thereafter. Because Down syndrome affects a child physically, there will be certain features that an alert doctor or nurse will pick up on. Most children with the syndrome will have some or all of these traits.

Common Physical Characteristics of Down Syndrome:

1) low muscle tone;

2) small nose and flat nasal bridge;

3) an upward slant to the eyes (almond shaped);

4) small skin folds on the inner corner of the eyes;

5) tongue large for size of child's mouth;

6) small, sometimes abnormally shaped ears;

7) a single crease across the center of the palm;

8) fifth finger, the pinky, has only one crease instead of two;

9) larger than normal space between the large and second toe;

10) joints are hyper flexible, able to extend greater than average.