What is Trisomy 21?

N. Madison
N. Madison

Trisomy 21, also referred to as Down Syndrome, is a chromosome abnormality caused by an extra copy of chromosome 21. Individuals with this condition usually have mental retardation, although other health issues may be present as well. This is a common birth defect, appearing in about one out of every 660 newborns.

Chest x-rays are used in the diagnosis of cardiac abnormalities.
Chest x-rays are used in the diagnosis of cardiac abnormalities.

Individuals with trisomy 21 are typically recognizable based on some specific physical characteristics. A child with Down Syndrome may have a head that is smaller than typical. His facial features may include upward slanting eyes, out of the ordinary for his family and ethnic group, a flattened nose, and a protruding tongue. There may be a rounded fold of skin in the inner corner of his eyes. Wide hands with short fingers are typical, as well as palms with a single crease, rather than multiple creases.

Trisomy 21 results when a baby has three rather than the typical two copies of chromosome 21 in all of his or her cells.
Trisomy 21 results when a baby has three rather than the typical two copies of chromosome 21 in all of his or her cells.

These children typically experience retarded growth and slower-than-normal development, and they usually do not reach typical adult heights. Individuals frequently have congenital heart defects and early death may occur as a result. Iris lesions, affecting the colored portion of the eye, may be seen as well. An individual with trisomy 21 may also present with a separation of the joints between the skull bones.

Individuals with trisomy 21 often have gastrointestinal abnormalities.
Individuals with trisomy 21 often have gastrointestinal abnormalities.

Gastrointestinal abnormalities are also common among these individuals. For example, obstruction of the esophagus or duodenum is fairly common and some cases are serious enough to require surgical intervention. Also, people with Down Syndrome are diagnosed with acute lymphatic leukemia, a malignant and potentially deadly cancer, at a higher rate than other children. About 80% of affected children are cured, however, thanks to advances in modern medicine.

Children with trisomy 21 typically experience retarded growth and slower-than-normal development.
Children with trisomy 21 typically experience retarded growth and slower-than-normal development.

There are many tests used to diagnose trisomy 21 and the conditions related to it. Chromosome studies are used to detect extra copies of the 21st chromosome. Chest X-rays and electrocardiograms are used in diagnosing cardiac abnormalities, and gastrointestinal C-rays are used to detect defects in this area when symptoms suggest an obstruction. For example, if an infant suffers from unusual vomiting, a medical professional may decide to use special X-rays to determine whether an obstruction is present.

Currently, there is no treatment or cure for this condition. Instead, treatments are aimed at fixing medical conditions that occur as a result of the syndrome. Treatment may include special education for individuals with mental handicaps and developmental delays. Individuals may also need to attend regular screenings to detect health issues, since they are more susceptible to certain types of infections.

Trisomy 21 is the most common cause of Down syndrome.
Trisomy 21 is the most common cause of Down syndrome.
N. Madison
N. Madison

Nicole’s thirst for knowledge inspired her to become a wiseGEEK writer, and she focuses primarily on topics such as homeschooling, parenting, health, science, and business. When not writing or spending time with her four children, Nicole enjoys reading, camping, and going to the beach.

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Discussion Comments

SteamLouis

@biva -- Experts are still studying fertility in individuals with trisomy 21 or down syndrome. While some have found that both sexes have significantly impaired fertility, it is also found that females with down syndrome are usually able to get pregnant. It must be noted however that due to health complications in individuals with Down's syndrome, there are increased risks in pregnancy and delivery.

burcinc

Did you know that Trisomy 21 screening can be done before birth? I learned this when I was pregnant with my first son. They can do all sorts of tests for it -- I think my doctor did something called a nuchal translucency ultrasound, though amniocentesis is more common -- during the first few months of pregnancy to check for down syndrome.

In fact, Down's syndrome screening is widely recommended by doctors to all pregnant women, especially because the risk of having a child with down syndrome is significantly higher for women of age 35 and older.

biva

Can the 21 trisomy baby grow sexually like the normal babies?

21 trisomy male person can marry? And will he be a father after marriage?

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