Down syndrome is the most common chromosomal condition in the United States, affecting about 1 in 700 babies.
In this article, Ability Central clarifies Down syndrome facts and myths by answering 8 frequently asked questions, including:
What is Down syndrome?
What are the types of Down syndrome?
What causes Down syndrome?
What are the physical characteristics of Down syndrome?
What are the behavioral and cognitive characteristics of Down syndrome?
What is the difference between Down syndrome and autism?
What other health conditions often accompany Down syndrome?
How is Down syndrome diagnosed?
Where can I get more information about Down syndrome?
What is Down Syndrome?
Down syndrome is named after the English physician John Langdon Down who first categorized the condition in 1866. The National Down Syndrome Society (NDSS) describes “Down syndrome” as the preferred name for the condition, but you may also have heard it called:
Downs syndrome
Down’s syndrome
Down’s child or Downs child syndrome
The genetic condition causes physical, intellectual, and developmental delays or disabilities. In addition, people with Down syndrome often share physical characteristics like flat, round faces, heart defects, or difficulties with digestion.
Most people are born with 46 chromosomes, the basic DNA code held in the nucleus of every cell. Down syndrome occurs through a process called “non-disjunction,” where the two copies of chromosome 21 do not separate during egg formation. If the egg becomes fertilized, the resulting baby has three copies of chromosome 21 in each cell.
The extra chromosome associated with Down syndrome leads to a range of mental, physical, and developmental differences.
What are the Types of Down Syndrome?
There are three types of Down syndrome. All three share physical and behavioral symptoms that are so similar researchers must inspect a person’s DNA to see the difference.
Trisomy 21. About 95% of people with Down syndrome have trisomy 21. This type of Down syndrome, sometimes called trisomia 21 or trisomie 21, causes each cell in the body to create three separate copies of chromosome 21 instead of the usual two.
Mosaicism (or mosaic Down syndrome). This form of Down syndrome is a mixture of two types of cells, some containing the usual 46 chromosomes and some containing 47. The cells with 47 chromosomes have an extra copy of chromosome 21. Mosaic down syndrome accounts for 2% of all cases.
Translocation Down syndrome. This rare type of Down syndrome occurs when an extra part of whole chromosome 21 is present but is attached to a different chromosome rather than a separate chromosome 21.
To learn more about the symptoms of Down syndrome, see 8 Ways to Recognize Down Syndrome: Symptoms, Warning Signs, and Diagnosis.
What Causes Down Syndrome?
Researchers still aren’t sure what causes Down syndrome.
Although Down syndrome is a genetic disorder, only 1% of Down syndrome births have a hereditary component (or in other words, 99% of babies with Down syndrome come from parents with typical chromosomes).
According to the National Down Syndrome Society (NDSS), the mother’s age is the only known factor linked to an increased chance of having a baby with trisomy 21 or Mosaicism. However, women under age 35 give birth to around 51% of babies with Down syndrome, so this link is still being explored.
According to recent Down syndrome facts and statistics:
A 35-year-old woman has about a 1 in 350 chance of conceiving a child with Down syndrome.
This chance increases gradually to 1 in 100 by age 40.
At age 45, the risk is 1 in 30.
Around 5% of Down syndrome cases come from a genetic link to the baby’s father.
The mother’s age does not seem to be linked to the risk of translocation Down syndrome. Instead, extra genes in one parent’s egg or sperm might cause translocation or, in rare cases, translocation Down syndrome can happen by chance.
In addition, siblings of a child with Down syndrome have a higher chance of developing the disorder, too.
What are the Symptoms of Down Syndrome?
Down syndrome is a genetic condition that affects development in multiple areas. Some of the most common symptoms of Down syndrome include learning difficulties, behavioral challenges, and round, flat faces with almond-shaped or up-slanted eyes.
Compared to people without the condition, people with Down syndrome may experience:
Physical differences
Language delays
Cognitive delays
Intellectual and developmental disabilities (I/DD)
Behavioral challenges
To learn more about the symptoms and physical characteristics of Down syndrome, see 8 Ways to Recognize Down Syndrome: Symptoms, Warning Signs, and Diagnosis.
How does Down Syndrome Affect Communication?
Down syndrome impacts cognitive and developmental skills like learning language and forming speech sounds, which can affect communication in unique ways.
Many people with Down syndrome have an easier time understanding what people say than they do making themselves understood. This is because their receptive language skills (figuring out words and concepts given to you) tend to be higher than their expressive language skills (explaining your own thoughts, feelings, and wishes to others).
People with Down syndrome often use basic “emerging language” skills to communicate, like:
Short, simple, or choppy sentences
Nonverbal methods like gestures or sign language
Grunts or noises rather than words
Repetition (like echolalia)
AAC devices like text-to-speech software, communication boards, or image-based communication apps
The most effective method of communication is to meet the person where they’re at. If there is a certain communication method that works for your loved one with Down syndrome, make that option available as often as possible.
What is the Difference Between Down Syndrome and Autism?
Autism and Down syndrome are not the same thing, but someone can be diagnosed with both disorders. In fact, around 1 in 5 people with Down syndrome also have autism.
Autism spectrum disorders (ASD or autism) is a neurodevelopmental disorder that affects social skills, perception, and behavior.
Down syndrome, on the other hand, is a genetic developmental disorder that affects someone’s body as well as their cognitive and social skills. Like autism, Down syndrome symptoms can be mild or severe, but Down syndrome is not part of the autism spectrum.
To learn more about co-occurring conditions like an autism and Down syndrome dual diagnosis, see The 7 Most Important Things To Do After a Down Syndrome Diagnosis.
What Health Issues Often Accompany Down Syndrome?
Some of the more common health problems among children with Down syndrome include:
Hearing loss
Obstructive sleep apnea
Ear infections
Eye diseases
Heart defects present at birth
Gastrointestinal issues (difficulties with food sensitivities and digestion)
Mental health problems, particularly for adults and teenagers with Down syndrome
Many of these, including hearing loss and eye diseases, can have a profound effect on a person’s ability to communicate effectively. This can greatly reduce independence for someone with Down syndrome, and often lead to being left out, bullied, or discriminated against.
In addition, people with Down syndrome have a higher chance of developing Alzheimer’s disease or dementia.
Elder care for people with I/DD can be complicated, so make sure to check out Long-term Success and Support for People With Down Syndrome for more resources.
How is Down Syndrome Diagnosed?
Doctors offer screening and diagnostic tests to mothers at certain points in their pregnancy. Screening tests estimate the likelihood that a child will be born with Down syndrome, and diagnostic tests confirm if the baby has Down syndrome.
In addition, certain tests can diagnose or confirm Down syndrome after the child is born.
See 8 Ways to Recognize Down Syndrome: Symptoms, Warning Signs, and Diagnosis to learn more about pregnancy screening for Down syndrome and other testing options.
Where Can I Get More Information About Down Dyndrome?
Ability Central offers a series of articles to further your knowledge about Down Syndrome. See:
8 Ways to Recognize Down Syndrome: Symptoms, Warning Signs, and Diagnosis
The 7 Most Important Things To Do After a Down Syndrome Diagnosis
Additional Information
The content provided in this article is for informational purposes only and is not intended as a substitute for legal, medical, or other professional advice. While we strive to provide accurate and up-to-date resources, some information may become outdated or incomplete. Always consult with your provider about personal medical concerns.
