Down Syndrome

What is it

Down syndrome is a genetic disorder in which a person is born with part of or a full extra chromosome. A chromosome is a thread-like structure within the nucleus of cells, carrying the genetic material of an organism. Typically, a person has 46 chromosomes (23 pairs) but individuals with down syndrome are born with 47 chromosomes (a partial or additional copy of chromosome 21). This often causes mental and physical development issues. Down Syndrome was discovered in the late nineteenth century by John Langdon Down, an English physician, who accurately described Down syndrome and recognized these features as their own condition. Today, about 6,000 babies with Down syndrome are born in the U.S. every year.

Symptoms

It is important to recognize that each individual with Down syndrome is unique: not every patient has the same physical features or the same range of cognitive or developmental difficulties. Some physical features that those with Down syndrome might have are:

Flattened face
Short head and neck
Upward slanting eyes
Small, white spots in the iris (colored part of the eye)
Small hands and feet
Poor muscle tone
Shorter height as children and adults

In addition to physical symptoms, people with Down syndrome may also have cognitive impairments, with symptoms ranging from mild to moderate. These impairments consist of delays in learning speech and language and short-term and long-term memory deficits.

Causes + Different Types

While the reasons for why some people are born with a partial or additional chromosome are not known, researchers have identified certain factors that increase the likelihood of being born with Down syndrome. One such factor is maternal age. Research indicates that women over the age of 35 are more likely to have pregnancies impacted by Down syndrome. However, more children with Down syndrome are born of women of younger ages primarily because younger age groups are more likely to have children. People with a family history of Down syndrome or those who have already given birth to a child with Down syndrome also have an increased chance of having a pregnancy affected by Down syndrome

There are 3 different types of Down Syndrome.

Trisomy 21: A trisomy 21 is the cause of Down Syndrome about 95% of the time. ‘Trisomy’ is the medical term for having an extra copy of a chromosome; thus, a person with Trisomy 21 has an extra copy of chromosome 21.

Translocation Down Syndrome: This is a type of Down Syndrome in which a person has two copies of chromosome 21 but additional genetic material from this chromosome is attached (translocated) to another chromosome. Whenever a translocation chromosome is found in a child, the parents’ chromosomes are also examined because there is a chance that the translocation was inherited. The difference between patients with Trisomy 21 and Translocation Down Syndrome is small.

Mosaic Down Syndrome: This is a rare form of Down Syndrome in which only some cells have an extra copy of chromosome 21, while other cells have the standard amount of chromosomes. Individuals with Mosaic Down Syndrome typically (but not always) have fewer or milder symptoms of Down Syndrome.

Diagnosis & Testing

Whether a child will be born with Down syndrome can be diagnosed to some extent during the pregnancy using either screening or diagnostic tests.

Screening Tests: These tests use blood tests (which measures various substances in the mother’s blood; abnormal amounts of any of these substances may point to a genetic condition) and ultrasounds (which generates an image of the fetus; specifically, doctors examine whether there is extra fluid behind the baby’s neck as an indicator for Down syndrome) to determine the likelihood of Down syndrome or other medical conditions in the baby. Other tests might be suggested based on the results of these tests but the screening tests themselves are not diagnostic.

Diagnostic Tests: These tests can identify whether the fetus has Down syndrome with almost 100% accuracy but are slightly more risky for the mother and the fetus because they require using a needle to acquire a sample from the uterus. These tests include:
- Chorionic villus sampling (CVS): this is a prenatal diagnosis method that examines tissue from the placenta and is used to detect conditions that include chromosomal abnormalities, such as Down syndrome.
- Amniocentesis: A needle into the amniotic sac (that surrounds the baby) and the fluid within is examined for any chromosomal abnormalities.
- Percutaneous umbilical blood sampling (PUBS): This text examines a fetal blood sample by drawing blood from the umbilical cord.

Down syndrome can also be diagnosed after the baby is born. The initial diagnosis is given by conducting a physical examination of the baby and identifying any physical features that are typically associated with Down syndrome. This diagnosis can then be confirmed with a chromosomal karyotype test that uses a blood sample to identify the child’s chromosomes. This test can also identify the type of Down syndrome the child has.

Treatment

While there is no cure for Down syndrome, there are a wide range of physical and developmental support that can be offered to patients. Once again, each child with Down syndrome is different and has different needs. Some might need occupational therapy to improve their motor skills, others might need physical therapy or speech therapy to increase muscle strengths and improve communication skills, respectively. Regardless of what the child needs, studies show that they will experience the most improvements when given access to support from a very young age. This is why it is important to get children screened early (if they have not already been diagnosed at birth) and get them this support. Additionally, Down syndrome might be accompanied by other complications, some of which can be treated or addressed with medication.

Other Complications

Those with Down syndrome are at an increased risk for certain health problems. These include but are not limited to:

Heart Defects: About 50% of patients with Down syndrome have heart defects which can lead to high blood pressure in the lungs, reduced oxygen in the blood, and an inability to efficiently pump blood.
Blood Disorders: Down syndrome can cause abnormalities in blood cells, which can lead to blood cancer.
Immune System Problems: Down syndrome causes problems in the immune system that make it harder for the body to fight off infections.
Vision and Hearing Issues: A large percentage of those with Down syndrome can develop eye disease or experience hearing loss.
Hypothyroidism: The thyroid is a gland in the body that produces hormones to regulate temperature and energy. Hypothyroidism, a condition in which the body makes few or no thyroid hormones, occurs more frequently among patients with Down syndrome.