What is Down Syndrome?

Down Syndrome is a medical condition first described in the literature by Dr. John Langdon Down in 1866. The word "syndrome" comes from Latin meaning "running together". The term is used in the medical context when a number of distinct physical features are seen together in one individual. Dr. Down first described individuals with this condition due to the upslant of their eyes, flat facial features, unusual creases in their hands, and impairment in their growth and mental development.

The newborn baby with Down Syndrome will show these features and may also appear floppy (low muscle tone) and be difficult to feed. The poor muscle tone from birth will impact the baby’s movement, strength and development. Mental development will also be delayed. Most children with Down Syndrome score within the mild to moderate range of mental retardation, with incredible variability from child to child. Individuals with Down Syndrome learn new skills more slowly, and differently, and have problems in applying what is learned. However, it is important to remember that they can learn and once they master a skill they don’t forget. Early and supportive interventions (physical, occupational and speech therapy) will maximize their learning potential.

Down Syndrome is the most common genetic cause of mental retardation. Approximately 1 out of every 700 children born has this condition. It occurs in every country around the world and in every racial and social group. Most people with Down Syndrome are born into a family with no other close relatives with the same condition. Therefore, it usually (95% of the time) is not inherited. Moreover, it is important to understand that this condition is not caused by anything that either parent did before or during the pregnancy. Down Syndrome is chromosomal in nature.

As you recall, chromosomes carry our genetic material that we pass on to our offspring. The mother and father each pass on half of their genetic material, in the form of 23 chromosomes, each time they conceive a child. The developing baby needs to have just the right amount of chromosomes in order to have normal growth and development. The magic number is 46 chromosomes, 23 from the mother and 23 from the father.

Individuals with Down Syndrome have 47 chromosomes, not 46, with an extra number twenty-one (21) chromosome. This extra chromosome, with the additional genetic material, produces the distinct physical features and developmental delays in an individual with Down Syndrome.

The Greenwood Genetic Center has a monthly Down Syndrome referral clinic to evaluate and make recommendations about interventional therapies and medical care issues for people of all ages with this condition.