Down Syndrome

By: Natalie Brennan

What is Down syndrome?Down syndrome is a

genetic condition in which a person has 47

chromosomes instead of the usual 46.

This disorder causes mental retardation and

other problems.

Down syndrome ranges in severity, so

developmental problems may range from mild to serious.

Causes of Down syndromeThere are 3 possible abnormalities which all result in extra genetic

material from chromosome 21,which causes Down syndrome.

1Trisomy 21• More than 90 percent of cases

with Down syndrome are caused by Trisomy 21.• With Trisomy 21 there are 3 copies of chromosome 21, instead of the usual 2 copies.

2Mosaic Down syndrome

• rare form of Down syndrome• With Mosaic Down syndrome some cells have an extra copy of chromosome 21, but not all.• Mosaic Down syndrome is caused by abnormal cell division after fertilization.

3Translocation Down syndrome

• occurs when part of a chromosome 21becomes attached onto another chromosome, before or at conception.• Children with Translocation have the usual 2 copies of chromosome 21, but have additional material from chromosome 21 stuck to the translocated chromosome.

MOST cases of Down syndrome are NOT inherited.

Common physical signs of Down syndrome

Individuals with Down syndrome have a widely recognized appearance.

Common physical signs include:• flattened nose• small ears• small mouth• upward slanting eyes• wide, short hands with short fingers• separated joints between the bones of the

skull• decreased muscle tone at birth• protruding tongue • small head

Risk FactorsAdvance Maternal Aging

A woman’s chance of giving birth to a child with Down syndrome

increases with age.

• Age 35 = 1 in 385 chance• Age 40 = 1 in 106 chance• Age 45 = 1 in 30 chance

Women who already have a child with Down syndrome typically have a 1 % chance of having another child

with Down syndrome.

Parents who are carriers of the translocation for Down syndrome can pass the genetic translocation

onto their children.

Statistics about Down syndrome

• about 1-in-800 risk overall for all births• 340,000 people in USA• 88% of cases arise from mother's chromosome 21; 8% from father's chromosome 21; 2% from mitotic errors after fusion• 66-88% of down patients have some level of hearing loss in at least one ear• 40 to 50% of children with Down syndrome have congenital heart defects in the US

Tests and Diagnosis The most efficient two step

screening is done during the 11th week and 14th week of pregnancy.

First the doctor does an ultrasound to get results, those

results are then paired with blood tests.

“When this two-step screening is done during the 11th week of pregnancy, researchers say it can identify 87 percent of babies with Down syndrome.”

If a screening test indicates a high chance of Down syndrome, more tests are done to see if the baby

actually had Down syndrome.

Tests for positive resultsIf your tests came back positive or are at a high risk for Down

syndrome, you can have further testing.

Amniocentesis• A sample of amniotic fluid is withdrawn from the mother’s fetus, this sample is used to analyze the chromosomes of the fetus.•The chance of miscarriage from taking this test is 1 in 200.

Chorionic villus sampling (CVS)•To analyze the fetal chromosomes, cells are taken from the mother’s placenta. •The risk for miscarriage by taking this test is 1 in 100.

Percutaneous umbilical blood sampling (PUBS)• To exam for chromosomal defects, blood is taken from the vein in the umbilical cord.•This test has a greater risk for miscarriage than both Amniocentesis and CVS.• Test usually is only done if completely necessary.

Complications with Down Syndrome

Children with Down syndrome are more likely to have complications. There is a range listed below.

Heart Defects

Leukemia Infectious

Diseases

Dementia

Famous people with Down syndrome

Chris Burke Jane Cameron

Sujeet Desai

Bernadette Resha

Never set limitations for yourself.

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