CONDITIONS

Down’s syndrome

Down syndrome is a genetic disorder that causes physical problems and intellectual disabilities. It is most often caused by the presence of an extra copy of chromosome number 21. This condition is called Trisomy 21.

Each person born with Down syndrome is different. Some have health problems. These could include heart disease, hearing problems, or problems with their intestines. Many begin treatment for medical issues early and live full, healthy, productive lives.

Causes

Down syndrome is caused by a problem during cell division. This results in extra genetic material. The extra genetic material causes the features and problems of Down syndrome. There are 3 types of Down syndrome:

• Trisomy 21.In this form, the cell division issue happens during the development of the sperm or the egg. This gives the child three copies of chromosome 21 instead of the normal two copies. Up to 95% of people with Down syndrome have Trisomy 21.
• Mosaic Down syndrome.Some cells have an extra copy of chromosome 21 because of abnormal cell division in the embryo. This form is rare. Only 1% of Down syndrome cases are Mosaic.
• Translocation Down syndrome.Translocation (or shift) occurs before or at conception when part of chromosome 21 attaches onto another chromosome. It is the only form of Down syndrome that can be passed down from parent to child. This can happen even if the parent shows no symptoms of Down syndrome.

There are factors that increase your risk of having a child with Down syndrome:

• Advanced maternal age.The older the woman is, the older her eggs are. Older eggs are more likely to divide abnormally. At age 35, your risk of having a baby with Down syndrome is about 1 in 350. At age 40, the risk is 1 in 100. By age 45, your risk is 1 in 30.
• Already having a child with Down syndrome.If you have a baby with Down syndrome, you have a 1 in 100 chance of having another one.
• Being acarrier of a chromosomal abnormality. Both men and women can carry the translocation abnormality. If you are a carrier, you risk passing it on to your child.

Symptoms

The symptoms of Down syndrome vary from person to person, and people with Down syndrome may have different problems at different times of their lives.

Physical Symptoms

Common physical signs of Down syndrome include1,2:

• Decreased or poor muscle tone
• Short neck, with excess skin at the back of the neck
• Flattened facial profile and nose
• Small head, ears, and mouth
• Upward slanting eyes, often with a skin fold that comes out from the upper eyelid and covers the inner corner of the eye
• White spots on the colored part of the eye (called Brushfield spots)
• Wide, short hands with short fingers
• A single, deep, crease across the palm of the hand
• A deep groove between the first and second toes

In addition, physical development in children with Down syndrome is often slower than development of children without Down syndrome. For example, because of poor muscle tone, a child with Down syndrome may be slow to learn to turn over, sit, stand, and walk. Despite these delays, children with Down syndrome can learn to participate in physical exercise activities like other children.3 It may take children with Down syndrome longer than other children to reach developmental milestones, but they will eventually meet many of these milestones.

Intellectual and Developmental Symptoms

Cognitive impairment, problems with thinking and learning, is common in people with Down syndrome and usually ranges from mild to moderate. Only rarely is Down syndrome associated with severe cognitive impairment.1

Other common cognitive and behavioral problems may include1,2,3,4:

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

Most children with Down syndrome develop the communication skills they need, although it might take longer for them to do so compared with other children. Early, ongoing speech and language interventions to encourage expressive language and improve speech are particularly helpful.

Diagnosis

Screening for Down syndrome is a normal part of prenatal care. Screening options include:

• Ablood test and ultrasound during the first trimester. The blood test looks for markers of abnormalities that could indicate Down syndrome. The ultrasound looks at “nuchal translucency.” It detects fluid at the back of the fetus’s neck. This could indicate an abnormality, including Down syndrome.
• A blood test in the second trimester.This is called the “triple screen” or “quad screen.” It also looks for markers in the mother’s blood.
• Integrated (combined) test.This approach uses the blood test and ultrasound from the first trimester and the blood test from the second trimester. It comes up with an overall risk rating of Down syndrome.

None of the screenings can diagnose Down syndrome. They only indicate that your risk of having a baby with Down syndrome is higher. Some women test positive in the screen but have perfectly healthy babies.

The only way to diagnose Down syndrome before birth is through diagnostic testing. This involves checking the tissue and fluid in the womb for the extra chromosome. This can be done through:

• Chorionic villus sampling (CVS).This takes a sample of the placenta during weeks 10 to14 of pregnancy.
• This takes a sample of the amniotic fluid during weeks 14 to 18 of pregnancy.
• Percutaneous umbilical blood sampling (PUBS).This is also called cordocentesis. It takes a sample of the fetal blood in the umbilical cordduring weeks 18 to 22 of pregnancy. It is the most accurate test.

There is a slight risk that these tests can cause a miscarriage. So these tests are used only when there is a higher chance of a genetic problem in the baby. This could be if the mother is 35 or older or if you have received an abnormal screening result. After birth, your doctor can test the baby’s blood for the extra chromosome. This is done if the baby has any of the physical signs or birth defects of Down syndrome.