People with Down syndrome are born with an extra chromosome, which changes the way their brain and body develop.
Down syndrome is a genetic disorder. Most babies are born with 23 pairs of chromosomes within each cell for a total of 46. A chromosome is a structure that contains genes, which are made up of your DNA. Genes determine how you form and develop growing in the womb and after birth. The majority of babies with Down syndrome are born with an extra copy of chromosome 21, with three copies of the chromosome instead of the usual two.
As a result, people born with Down syndrome face some physical and mental challenges throughout life. They typically have distinctive body and facial features that set them apart. They are more likely to develop slowly, and are more at risk for some medical conditions.
Yes, there are three types of Down syndrome. They are:
. Trisomy 21: The term “trisomy” means having an extra copy of a chromosome. The most common type of Down syndrome, trisomy 21, occurs when a developing baby has three copies of chromosome 21 in every cell instead of the typical two copies. This type makes up 95% of the cases.
. Translocation: In this type of Down syndrome, there is an extra full or partial amount of chromosome 21 attached to another chromosome. Translocation accounts for 4% of the cases.
. Mosaicism: In the rarest type (only 1%) of Down syndrome, some cells contain the usual 46 chromosomes, and some contain 47. The extra chromosome in these cases is chromosome 21.
Researchers are unsure why Down syndrome occurs in certain people. Anyone of any race or societal level can be affected.
What is known is that the risk of giving birth to a child with Down syndrome increases as women grow older. Women aged 35 and older are more likely to have their pregnancy affected by the syndrome. But because younger women have higher fertility rates, most babies with Down syndrome are born to women under 35.
Each human cell typically contains 23 pairs of chromosomes. Down syndrome occurs because of changes in the way cells in chromosome 21 divide. Every person with Down syndrome has an extra amount of this chromosome in some or all of their cells.
In the most common type of Down syndrome, trisomy 21, the condition occurs randomly and isn’t inherited. However, when translocation or mosaicism is the cause of Down syndrome, hereditary (passed down among family members) should be looked at as a cause.
Down syndrome causes physical, cognitive (thinking) and behavioral symptoms.
Physical signs of Down syndrome can include:
. Short, stocky physical size, with a short neck.
. Poor muscle tone.
. Flattened facial features, especially the bridge of the nose.
. Small ears.
. Almond-shaped eyes that slant upward.
. Small hands and feet.
. Single deep crease across the center of the palm of the hand.
Common learning and behavioral symptoms of Down syndrome include:
. Delays in speech and language development.
. Attention problems.
. Sleep difficulties.
. Stubbornness and tantrums.
. Delays in cognition.
. Delayed toilet training.
Not all people with Down syndrome have all these symptoms. Symptoms and their severity are different from person to person.
Your healthcare providers can diagnose Down syndrome before your baby is born or at birth.
. In prenatal (before birth) tests called screenings, blood tests and ultrasound (imaging test) are used to look for “markers” that suggest Down syndrome may be present.
. Other prenatal screenings used to diagnose Down syndrome include amniocentesis and chorionic villus sampling (CVS). In these tests, a doctor removes a sample of cells from the part of the womb called the placenta (CVS), or the fluid surrounding the baby (amniocentesis), to look for abnormal chromosomes. You can choose whether or not to have these prenatal screenings.
. At birth, providers look for the physical signs of Down syndrome. To confirm the diagnosis, a blood test called a karyotype is done. In this test, a small sample of blood is taken and studied under a microscope to see if an extra amount of chromosome 21 is present.
If you find out the baby you’re carrying has Down syndrome, your providers will direct you to resources to help you after your child’s birth. Several options are available (see Resources section).
You may want to participate in counseling or join a support group. Counselors and support groups help you prepare for raising a child with Down syndrome.
In support groups you can talk with other parents about their experiences living with Down syndrome. It’s a great way to share practical advice on coping with the condition, its ups-and-downs, frustrations and joys. You’ll find that you’re not alone.
Down syndrome can’t be prevented, but parents can take steps that may reduce the risk. The older the mother, the higher the risk of having a baby with Down syndrome. Women can reduce the risk of Down syndrome by giving birth before age 35.
Treatment for Down syndrome varies. It typically starts in early childhood. The purpose is for you and your child with Down syndrome to learn to cope with the condition, as well as treat what physical and cognitive (thinking) challenges arise.
Your providers may help you develop a care team for your family member with Down syndrome. The care team may include:
. Primary care providers to monitor growth, development, medical concerns and provide vaccinations.
. Medical specialists depending on the needs of the person (for example, cardiologist, endocrinologist, geneticist, hearing and eye specialists).
. Speech therapists to help them communicate.
. Physical therapists to help strengthen their muscles and improve motor skills.
. Occupational therapists to help refine their motor skills and make daily tasks easier.
. Behavioral therapists to help manage emotional challenges that can come with Down syndrome.
People with Down syndrome often have associated medical conditions that are either present at birth or develop over time. These can often be managed by medications or other care. Common conditions of Down syndrome can include:
. Heart problems, frequently present at birth.
. Thyroid abnormalities.
. Hearing and vision problems.
. Low fertility rate in males with the syndrome. Around 50% of women with Down syndrome are able to bear children, but the risk of the child having the condition is between 35%-50%.
. Sleep apnea.
. Gastrointestinal problems, like constipation, gastroesophageal reflux (when fluid from the stomach re-enters the esophagus) and celiac disease (intolerance for wheat protein).
. Autism, with challenges with social skills, communication and repetitive behaviors.
. Alzheimer’s disease, which causes memory and thinking problems in older age.
No. Down syndrome is a lifelong condition and right now there isn’t a cure. But many health problems associated with the condition are treatable.
Many traits and conditions in people with Down syndrome are manageable with treatment and therapies. Medical care, support and education help them throughout their lives. Like anyone else, people with Down syndrome go to school, work, have meaningful relationships and can lead healthy and active lives.
Many people with Down syndrome live to age 60 or older.
Are people who have Down syndrome at greater risk for developing Alzheimer's disease?
People with Down syndrome are at greater risk for developing Alzheimer’s disease. According to the Down Syndrome Society, Alzheimer’s disease is diagnosed in about 30% with Down syndrome in their 50s and in about 50% of those in their 60s.
Studies show the extra full or partial chromosome contributes to this increased risk of Alzheimer’s. Genes on chromosome 21 produce amyloid precursor protein, which plays an important role in the brain changes seen in Alzheimer’s patients.