An Overview of Down Syndrome

Ms. Pregler

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What is Down Syndrome?

Down Syndrome is a set of physical and mental traits caused by a gene problem that happens before birth. It is the most commonly occurring chromosomal condition and it occurs in people of all reaces and economic levels.

It is caused by a problem with a baby’s chromosomes. Normally, a person has 46 chromosomes while most people with Down Syndrome have 47 chromosomes. This changes the way the brain and body develop.

Children with Down Syndrome tend to have similar facial features and some degree of intellectual disability. This varies from person to person, but in most cases is mild to moderate. Life expectancy is shortened from the average person, but has increased dramatically in recent years. In 1983, the average life expectancy for someone with Down syndrome was 25. Today it is 60.

What is the Genetic Cause of Down Syndrome?

Down syndrome is a genetic condition, but only 1% of all cases of Down syndrome have a hereditary component (passed from parent to child through the genes). Most cases occur result from mistakes during the meiotic process that forms the egg and sperm of the parents.

There are 3 types of Down syndrome:

Trisomy 21:

  • Most common form of down syndrome.
  • An extra copy of chromosome 21 is carried by either the egg or the sperm during fertilization. The result is 3 copies instead of the usual 2.
  • All cells in the developing offspring are affected.

Mosaic Down syndrome:

  • Children have some cells with an extra copy of chromosome 21. Caused by abnormal cell division after fertilization.

Translocation Down syndrome:

  • Chromosome 21 becomes attached onto another chromosome before or during fertilization
  • This type of Down syndrome can be inherited, meaning a parent may also have/carry the condition
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The picture above shows the results of typical cell division (meiosis).
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How is Down Syndrome Diagnosed?

Down syndrome is often diagnosed before the birth of the child, or prenatally. If it is not diagnosed before birth, it is usually diagnosed shorty after.

Prenatal Diagnosis:

  • Screening tests: These estimate the chance of a child being born with Down syndrome based on various traits, measurements, and levels of certain proteins. Screening tests usually use a combination of ultrasound technology and blood serum testing on the mother. Screening tests only provide a statistical chance of the baby being affected and are not 100% accurate.

  • Diagnostic tests: These tests include the CVS and amniocentesis. They analyze fetal cells for the extra chromosome and are nearly 100% accurate in diagnosis. Both tests carry a slight risk for miscarriage.

At Birth:

Down syndrome is usually identified at birth by the presence of certain physical traits like low muscle tone, a single deep crease across the palm of the hand, a slightly flattened facial profile and an upward slant to the eyes. Babies suspected of having Down syndrome will undergo a chromosomal analysis called a karyotype where the chromosomes are arranged and photographed. In Down syndrome, an extra chromosome in the 21st pair will be evident.

The picture above shows how meiosis differs in gametes that result in Down syndrome.

Are there any Risk Factors for Down Syndrome?

With the exception of maternal age (age of the mother), there are no specific risk factors for Down syndrome. It occurs in people of all races and economic levels

A 35 year old woman has about a 1 in 350 chance of conceiving a child with Down syndrome, A 40 year old woman has about a 1 in 100 chance.

What are the Symptoms of Down Syndrome?

Symptoms of Down syndrome vary from individual to individual. For reasons we do not fully understand, the extra chromosome can have mild, less severe complications in some people, and severe complications in others. Here is a list of the most common physical and intellectual symptoms.

Physical Symptoms

  • Decreased or poor muscle tone
  • Shorten neck, arms, and legs compared to body
  • Flattened facial profile and nose
  • Small head, ears, and mouth compared to body
  • Upward slanting eyes
  • Wide, short hands and short fingers
  • Lack of muscle tone
  • Likely heart defects
  • Slower physical development
  • Vision and hearing deficiencies
  • Thyroid problems
  • Risk of incomplete intestinal development
  • Increased risk of Leukemia
  • Prone to infection and illness

Intellectual and Developmental Symptoms

  • Short attention span
  • Poor judgement
  • Impulsive behavior
  • Slow learning
  • Delayed language and speech development

How Do We Treat Down Syndrome?

There is no single treatment for Down syndrome. Treatments are based on each individual’s physical and intellectual needs.

A Down syndrome child may receive and/or need

  • Special education
  • Speech and language therapy
  • Physical therapy to increase muscle development and motor skills
  • Occupational therapy to teach basic tasks
  • Job training
  • Social work/counseling for emotional needs
  • Surgery to correct a heart defect
  • Special diet due to digestive issues
  • Vision and hearing assistive devices

Where Can Someone Go for Additional Resources, Information, or Support?

National Down Syndrome Society

A national advocacy group with a wealth of information and resources.

National Association of Down Syndrome (NADS)

An Illinois based association with local events, support groups, and a library of information and resources.

Gigi's Playhouse

"GiGi’s Playhouse is all about achievement, belief and confidence. Serving children and adults of all ages, Playhouses across the country offer 30 educational and therapeutic programs at no charge to families. All programs aim to maximize self-confidence and empower individuals to achieve their greatest potential. Our literacy program alone teaches thousands of kids with Down syndrome to read every year! Founded by GiGi’s Mom in 2003 as a single location in Hoffman Estates, IL, GiGi’s Playhouse has grown into a strong network of 24 Playhouses including the first international Playhouse in Queretaro, Mexico. Last year, over 25,000 participants benefited from Playhouse programs."