Down syndrome is caused by a person having three copies of chromosome 21 instead of two copies. This is why Down syndrome is also referred to by the name Trisomy 21. The picture above shows a genetic analysis of a person with Down syndrome. You will notice that the arrow is pointing to the set of number 21 chromosomes. Instead of a pair of chromosomes, as is found in all the other chromosomes, number 21 includes three chromosomes. It is important to understand that all of the chromosomes of this person are normal. It is the fact that there is an extra chromosome that causes Down syndrome. Every cell in a person with Down syndrome will contain 47 chromosomes (with the exception of Mosaic Down syndrome which is discussed below) instead of 46 chromosomes. There are many theories about how the extra chromosome causes the effects of Down syndrome but little is currently known. Research, however, is continuing and a breakthrough may provide possible treatments to lessen the effects.


General characteristics

Most children with Down syndrome have some of the following physical traits:

• Short stature. A child often grows slowly and, as an adult, is shorter than average.
• Weak muscles (hypotonia) throughout the body. A child may seem to have less strength than other children
of the same age. Weak abdominal muscles also make the stomach stick out.
• A short, wide neck with excess fat and skin. Usually, this trait is less obvious as the child gets older.
• Short, stocky arms and legs. Some children also have a wide space between the big toe and second toe.
• A single crease across the center of the palms of the hands. This is called a transverse palmar crease or simian line.

Facial features

Down syndrome often results in distinct facial features, such as:

• Small, low-set ears.
• Irregularly shaped mouth and tongue. The child's tongue may partly stick out. The roof of the mouth (palate) may be narrow and high with a downward curve.
• A nasal bridge that looks pushed in. The nasal bridge is the flat area between the nose and eyes.
• Tissue buildup on the colored part of the eye (iris). These areas are known as Brushfield's spots
and do not affect the child's vision.
• Irregular and crooked teeth that often come in late and not in the normal sequence.

Other medical conditions

A child may have other medical conditions related to Down syndrome, such as:

• Intellectual disability. Most children with Down syndrome have mild to moderate cognitive disability.
• Heart defects. About half of the children who have Down syndrome are born with a heart defect.1 Most defects
are diagnosed at birth or shortly after birth.
• Diseases such as hypothyroidism, celiac disease, and eye conditions.

Children with Down syndrome are also prone to developing other health problems.
For example, respiratory infections, hearing problems, and dental problems are common.
Positives/ strengths of Down Syndrome:

people with Down syndrome routinely survive into their fifties and sixties
Many hold steady jobs in the workplace.




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