What is Down Syndrome?

Down syndrome is a genetic condition that results when a baby is born with three rather than the usual two copies of chromosome 21. Because there are three copies of chromosome 21, Down syndrome is also called “Trisomy 21.”

Trisomy 21, the most common type of Down syndrome, occurs when there are three, rather than two, number 21 chromosomes present in every cell of the body. Instead of the usual 46 chromosomes, a person with Down syndrome has 47. It is this additional genetic material that alters the course of development and causes the characteristics associated with the syndrome. Trisomy 21 accounts for 95 percent of cases.

Translocation occurs when 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. Translocation accounts for 4 percent of cases.

Mosaicism occurs when nondisjunction of chromosome 21 takes place in one — but not all — of the initial cell divisions after fertilization. When this happens, there is a mixture of two types of cells: some containing the usual 46 chromosomes and others containing 47. Mosaicism accounts for about 1 percent of all cases.

Down syndrome is the most frequently occurring chromosomal abnormality, occurring once in every 792 live births.

It is estimated that 250,000 people in the United States and about 4 million people worldwide have Down syndrome.

Down syndrome occurs equally in people of all ethnic, racial, religious, and socioeconomic groups.

The rate of births of children with Down syndrome increases with the age of the mother. While the age of the mother can be a factor, 80 percent of children with Down syndrome are born to parents under the age of 35.

Yes, people with Down syndrome have increased health risks.

• Approximately 40 to 60 percent of infants with Down syndrome have a congenital heart defect.
• Low muscle tone is common in people with Down syndrome. This may result in delayed gross motor development like crawling and walking. Also common is constipation and gastroesophageal reflux.
• Those with Down syndrome are at greater risk for childhood leukemia, sleep apnea, thyroid conditions, Alzheimer’s diseases, and diabetes. Many of these conditions are treatable, and most people with Down syndrome lead healthy lives.

Common traits include low muscle tone, small stature, an upward slant of the eyes, and a single, deep crease across the center of the palm. While there are similarities among people with Down syndrome, each person is unique and may possess these characteristics to varying degrees or not at all.

Social Awareness 

One of the objectives the Down Syndrome Association of Central Ohio (DSACO) seeks to accomplish is to raise awareness about Down syndrome. It is important that the misconceptions about this chromosomal disorder are corrected and, above all, that we call for all human beings – with or without disabilities – to be viewed in high regard and with dignity. 

The Proper Use of Language for Down syndrome: 

• Down vs. Down’s – National Down Syndrome Society (NDSS) uses the preferred spelling, Down syndrome, rather than Down’s syndrome. While Down syndrome is listed in many dictionaries with both popular spellings (with or without an “apostrophe S”), the preferred usage in the United States is Down syndrome. This is because an “apostrophe S” connotes ownership or possession. Down syndrome is named for the English physician John Langdon Down, who characterized the condition, but did not have it. The AP Stylebook recommends using “Down syndrome” as well. 

• People with Down syndrome should always be referred to as people first. Instead of “a Down syndrome baby”, it should be “a baby with Down syndrome”.  Also avoid “Down’s baby” and describing the condition as “Down’s” as in, “He has Down’s”. 

• Down syndrome is a condition or a syndrome, not a disease. 

• People “have” Down syndrome, they do not “suffer from” and are not “afflicted by” it. 

• While it is unfortunately clinically acceptable to say “mental retardation”, it is more socially acceptable “Intellectual disability”. Broadly, at a national, state and local level, the use of the word “retarded” is considered unacceptable, inappropriate language. Using this word is hurtful and suggests that people with disabilities are not competent.