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Understanding Down Syndrome

By Dr Zubair Abdulahi 29 October 2018   |   6:00 am

Down Syndrome is a genetic disorder in which there are extra sets of chromosome 21. Also called trisomy 21, Down syndrome was named after the discoverer, John Langdon Down, an English physician, and is characterised by varying degrees of intellectual disability.

Chromosomes are the means of passing genetic material from parents to their offsprings. Twenty-three (23) of these chromosomes are “donated” by each parent to form a complete set of forty-six (46) in the offspring(s). However, in Down syndrome, one of these chromosomes (chromosome 21) is duplicated fully or partially. This additional genetic material alters the course of development and causes the characteristics associated with Down syndrome.

Who is affected by Down syndrome?

There is no racial, economic or geographical predilection in the development of Down Syndrome. It is the most common chromosomal disorder in the world. It is also estimated that they deliver about 6,000 children with Down Syndrome in the United States alone, every year. It is estimated that there are over 5 million people living with Down Syndrome worldwide today.

What causes Down syndrome?

They have not identified the cause of the extra chromosome. Nothing done before or during pregnancy can cause Down syndrome. However, the commonest risk factor is the age of the mother at pregnancy with older women (>35) being more at risk. The risk of development increases from 0.1% in 20-year-old mothers to 3% in 45-year-old mothers.

What are the signs and symptoms of Down syndrome?

A few of the common physical traits of Down syndrome are low muscle tone, an upward slant to the eyes, and a single deep crease across the centre of the palm – although each person with Down syndrome is a unique individual and may have these characteristics to different degrees, or not at all.

Other features also are seen which may include: mild-to-moderate intellectual disability resulting in delayed milestones, stunted growth, flat head, large tongue, flattened nose and abnormal ears and teeth. They also have congenital heart disease in a large chunk of cases. 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.

At birth, Down syndrome can be diagnosed on physical examination of the newborn due to the characteristic features of the disorder and genetic testing.

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