Definition of Down syndrome taken from the National Down Syndrome Society (www.ndss.org).
It wasn’t until the late 19th century 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, which earned Down the recognition as the “father” of the syndrome. Although other had previously recognized the characteristics of the syndrome, it was Down who described the condition as a distinct and separate entity.
In 1959, the French physician, Jerome Lejeune, identified Down syndrome as a chromosomal anomaly when he observed 47 chromosomes present in each cell of individuals with Down syndrome instead of the usual 46. It was later determined that an extra partial or complete 21st chromosome results in the characteristics associated with Down syndrome.
Down syndrome occurs in one out of every 733 live births, and more than 400,000 people in the U.S. have this genetic condition. One of the most frequently occurring chromosomal abnormalities, Down syndrome affects people of all ages, races and economic levels. Today, individuals with Down syndrome are active participants in the educational, vocational, social, and recreational aspects of our communities. In fact, there are more opportunities than ever before for individuals with Down syndrome to develop.
An additional chromosome means that there is excess genetic material in the cells of individuals with Down syndrome. While this will affect the person’s development, it is important to realize that it is not a blueprint that determines his or her potential. As is true for all people, the skills and knowledge he or she acquires will be a unique combination of innate abilities and life experiences.
All people with Down syndrome experience cognitive delays. The effect is usually mild to moderate and is not indicative of the many strengths and talents that each individual possesses. Additionally, some people with Down syndrome have low muscle tone and other physical characteristics associated with Down syndrome that will likely affect how soon a child with Down syndrome will be able to sit up, walk, and speak. Although a child with Down syndrome will learn how to do these and many other activities, it may be somewhat later than his or her peers without Down syndrome.