What is Down syndrome?
Down syndrome is named after the English doctor, John Langdon Down, who was the first to categorize the common features of people with the condition. Dr. Jerome Lejeune discovered Down syndrome is a genetic disorder whereby a person has three copies of chromosome 21 instead of two. There are also very rare forms of Down syndrome (less than 6%) called Translocation Down Syndrome or Mosaic Down Syndrome in which not all of the chromosome is triplicated or not all cells of the body carry the extra chromosome.
Down syndrome is the most frequently occurring chromosomal disorder and the leading cause of intellectual and developmental delay in the U.S. and in the world.
What is the cause of Down syndrome?
The cause of Down syndrome is unknown. In a process called non-disjunction, the two copies of chromosome 21 fail to separate during formation of the egg, resulting in an egg with two copies of the chromosome. When this egg is fertilized, the resulting baby ends up with three copies of chromosome 21 in each of its cells. The cause of this non-disjunction remains unknown. Down syndrome probability increases with advanced age in mothers.
However, since younger women have more babies, 80% of newborns with Down syndrome in the US are born to mothers under 35 years old. Down syndrome has nothing to do with race, nationality, socioeconomic status, religion, or anything the mother or father did during pregnancy.
There is NO correlation between incest and Down syndrome. Between two and four percent of the time, a person is born with Mosaic translocation Down syndrome (mDs) whereby some but not all of the cells have an extra copy of the 21st chromosome and the other cells are not affected.
Translocation happens when a piece of chromosome 21 becomes attached to another chromosome during cell division.
In the case of hereditary Translocation Down syndrome (a rare one to two percent of all people with Down syndrome), an extra chromosome 21 is inherited from one of the parents.
What is the population of people with Down syndrome?
Some estimates put the worldwide population of people with Down syndrome at more than 6 million. More research is needed to ascertain whether this number is accurate.
In U.S, the average lifespan of a person with Down syndrome is approximately 60 years. As recently as 1983, the average lifespan of a person with Down syndrome was 25 years. The dramatic increase to 60 years is largely due to the end of the inhumane practice of institutionalizing people with Down syndrome. In the last several years, the average IQ of a person with Down syndrome has increased. In people with Down syndrome, 39.4% are in the mild intellectual disability range of 50-70, and 1% in the borderline intellectual function range of 70-80 (average IQ in the general population is 70-130). People with Down syndrome have physical and intellectual delays from birth but there is a wide variety of abilities within the population that are impossible to predict ahead of time.
A growing number of people with Down syndrome live independently. A small but growing number of people with Down syndrome are choosing to get married and live together.
How do medical issues and care affect people with Down syndrome?
People with Down syndrome are significantly predisposed to certain medical conditions including congenital heart defects, sleep apnea, and Alzheimer’s disease. There is also evidence of an increased risk of celiac disease, autism, childhood leukemia and seizures.
Some research shows that people with Down syndrome who have certain heart defects or childhood leukemia are more likely than their typical counterparts to recover or recover quickly. More research is needed to assess actual frequency and recovery of such medical conditions in the Down syndrome population. Many of these medical conditions can be treated, and many people with Down syndrome will not have these medical conditions.
It is rare for a person with Down syndrome to have a solid tumor cancer or cardiovascular disease, including heart attack and stroke. Although children and adults with Down syndrome may share some common features, they look more like their immediate family members than like each other.
Common but not universal features include short stature, round face, almond-shaped and up-slanting eyes.
Such features are not medical conditions. Appropriate medical care for children and adults with Down syndrome is very important. It can make a major difference for that person’s physical and intellectual development. Doctors are not always trained to provide the best medical care for a person with Down syndrome.
To help, you can recommend or print out the Health Supervision for Children with Down Syndrome or Healthcare Management of Adults with Down Syndrome guidelines.
Early intervention for babies with Down syndrome is very important. The appropriate physical and speech therapies for the first five years can make a major difference for that child’s physical and intellectual development.
How will a baby with Down syndrome affect one’s family?
It is understandable that parents are concerned about how a child with Down syndrome will affect their family, including siblings. Every family is unique and may deal with the idea of, or the birth of, a baby with Down syndrome differently.
Despite potential challenges, personal accounts and studies show that many families that have a child with Down syndrome are stable, successful and happy, and that siblings often have increased tolerance, compassion and awareness. In fact, a major study on marriages and Down syndrome shows the divorce rate among parents of children with Down syndrome is lower than the national average.
Source: Global Down Syndrome Foundation