Down Syndrome is a chromosomal disorder in which there is the presence of extra sets of chromosomes 21. Chromosomes are the means of passing genetic material from parents to their offspring.
They contain DNA and genetic materials that instruct the body on how to function. Twenty-three (23) of these chromosomes are “donated” by each parent to form a complete set of forty-six (46) in the offspring to determine their characteristics, for instance, whether they will be tall or short, have dark or light skin, curly or straight hair).
However, in Down’s syndrome (also called trisomy 21), one of these chromosomes (chromosome 21 specifically) is duplicated fully or partially leading to an extra set of chromosomes.
This duplication is responsible for the features of the disorder because the additional genetic material alters the course of development.
Down syndrome is characterized by varying degrees of intellectual disability and physical abnormalities.
What causes Down syndrome?
The cause of the extra chromosome has not been identified. Nothing done before or during pregnancy can cause Down syndrome.
However, some features increase the odds of having a child with Down syndrome. These features are called risk factors.
The commonest risk factors identified in the development of Down Syndrome are:
a. The age of the mother at pregnancy: Women older than age 35 are at a higher risk of having a child with Down syndrome than younger women. The risk of development increases from 0.1% in 20-year-old mothers to 3% in 45-year-old mothers.
b. Women who have Down syndrome have a 50% chance of having a child with Down syndrome. Men with Down syndrome are usually infertile.
Who is affected by Down syndrome?
Down syndrome is the most common chromosomal disorder in the world. The estimated incidence of Down syndrome is between 1 in 1,000 to 1 in 1,100 live births worldwide and around 5 million people are living with Down Syndrome worldwide today.
There is no racial, economic, or geographical predilection in the development of Down Syndrome. It is evenly spread across the globe but countries with prenatal screening and diagnosis (diagnosing Down syndrome when the pregnancy is ongoing) for Down syndrome are seeing less live births than those who do not have prenatal screening facilities.
What are the signs and symptoms of Down syndrome?
There are several physical signs seen in children with Down syndrome. There are also accompanying intellectual disabilities.
However, it is worthy of note to point out that each person with Down syndrome is a unique individual and may possess these characteristics to different degrees, or not at all. A few of the common physical traits of Down syndrome include:
● Low muscle tone,
● An upward slant to the eyes,
● Short and broad fingers.
● A single deep crease across the centre of the palm is often present.
● Stunted growth and an increased risk of being obese,
● Short stocky arms and legs,
● A flat head,
● Large tongue,
● Flattened nose and neck folds
● Abnormally small and rounded low set ears and abnormal teeth.
● They also have congenital (inborn) heart disease in around 50% of cases. There are also digestive system abnormalities in some children.
Other features also are seen which may include: mild to moderate intellectual disability resulting in delayed milestones, including walking and talking. There may also be behavioural problems.
Individuals with Down syndrome have an increased risk of developing several medical conditions.
How is Down Syndrome diagnosed?
Diagnosing Down syndrome can be done when the pregnancy is ongoing (prenatal) and at birth. Before birth, screening tests (blood tests and ultrasound scan) can be done to estimate the chances of the development of Down syndrome.
These tests are not definitive and the only way to confirm the diagnosis is via more invasive definitive tests (chorionic villus sampling and/or amniocentesis). These are also confirmatory tests of the chromosomal disorder.
At birth, Down syndrome can be diagnosed on physical examination of the newborn due to the characteristic features of the disorder and by carrying out genetic testing.
After confirmation of the diagnosis, other investigations are carried out to find any other abnormalities that may impair the health status of the child.
How is Down syndrome treated?
There is no cure for Down syndrome at this time. Associated conditions or symptoms can be managed. Most people with Down syndrome survive to adulthood and some of them show only mild symptoms, even with intellectual disability and physical abnormalities.