Trisomy 21: What is it , How is it Diagnosed, and What’s the Prognosis?

Every human being has 46 chromosomes split into 23 pairs. We inherit half our chromosomes (23) from each parent, and they group together to make a complete person. However, sometimes a fetus inherits fewer, or more, chromosomes than normal. This is known as a chromosomal abnormality. Luckily, we now have cell free DNA tests that can test for the presence of common genetic abnormalities such as trisomy 21 (Down Syndrome), which is common of all genetic abnormalities.

What is Down Syndrome?

Trisomy 21 cases are those in which the fetus has inherited an additional pair of chromosomes leaving them with a total of 47 as opposed to the normal 46. Trisomy 21 causes impaired mental and physical development, some of which can lead to medical complications later in life. Trisomy 21 (Down Syndrome) cases also tend to share certain physical characteristics, such as:

• Almond-shaped, slanted eyes;
• A flattened face;
• Small ears, hands, and feet;
• Short stature;
• A short neck;
• A protruding tongue; and,
• Poor muscle tone and loose joints.

There are actually three different types of this condition, although the physical and mental characteristics tend to be the same for all three.

• Trisomy 21 is the most common of the three, with nearly 95-percent of all cases being results of trisomy 21. This occurs when there are three copies of chromosome 21 grouped together.

Diagnosing Trisomy 21

Prior to the advent of fetal screening, trisomy 21 was diagnosed after the baby was born based on physical characteristics, and on genetic blood testing.

As screening became more advanced, doctors were able to diagnose the condition during pregnancy by taking a sample of the amniotic fluid, the “water” surrounding the baby in the womb. The amniotic fluid contains the fetal DNA and doctors use this fluid to check for chromosomal anomalies.

In recent years, doctors have begun to rely on cell free DNA testing to test for trisomy 21 as well as trisomies 18 and 13. These tests require a small amount of blood from the mother and don’t carry the same risk invasive prenatal procedures. The tests much be ordered by your healthcare provider, and are available within 5 days from the date the lab receives your sample.

Trisomy 21 Prognosis

Trisomy 21 cases tend to have an increased risk of developing a wide range of post-birth disorders such as pulmonary hypertension, which can damage the lungs, and should be evaluated by a cardiologist starting in childhood. It can also cause hearing issues, such as hearing loss from structural problems in the ear canal, or fluid buildup in the inner ear. There could also be vision problems such as an increased risk of cataracts, far- or nearsightedness, and strabismus.

Other, less frequent, medical complications include thyroid problems, seizure disorders, a higher risk of childhood leukemia, and intestinal abnormalities.

Although these types of pregnancies present a high risk of medical complications, some people affected have no significant health problems and are quite high functioning.

Some of those affected have been known to go on to become actors, college graduates, politicians, activists and business owners.

Conclusions

With the right care, people with this condition can overcome these complications. Additionally, although the condition can cause cognitive delays, these delays don’t have to interfere with their ability to achieve. Getting the proper screening tests can help parents prepare, so that they can give their children every opportunity to live long and productive lives.