Down Syndrome
Down syndrome is a genetic
disorder caused when abnormal cell division results in an extra full or partial
copy of chromosome 21. This extra genetic material causes the developmental
changes and physical features of Down syndrome. Down syndrome varies in
severity among individuals, causing lifelong intellectual disability and
developmental delays. It's the most common genetic chromosomal disorder and
cause of learning disabilities in children. It also commonly causes other
medical abnormalities, including heart and gastrointestinal disorders. Better
understanding of Down syndrome and early interventions can greatly increase the
quality of life for children and adults with this disorder and help them live
fulfilling lives.
Symptoms Each person with
Down syndrome is an individual — intellectual and developmental problems may be
mild, moderate or severe. Some people are healthy while others have significant
health problems such as serious heart defects. Children and adults with Down
syndrome have distinct facial features. Though not all people with Down
syndrome have the same features, some of the more common features include:
Flattened face, Small head, Short neck, Protruding tongue, Upward slanting eye
lids (palpebral fissures), Unusually shaped or small ears, Poor muscle tone,
Broad, short hands with a single crease in the palm, Relatively short fingers
and small hands and feet, Excessive flexibility, Tiny white spots on the
colored part (iris) of the eye called Brushfield's spots. Short height. Infants
with Down syndrome may be average size, but typically they grow slowly and
remain shorter than other children the same age.
Intellectual disabilities
Most children with Down syndrome have mild to moderate cognitive impairment.
Language is delayed, and both short and long-term memory is affected.
When to see a doctor
Children with Down syndrome usually are diagnosed before or at birth. However,
if you have any questions regarding your pregnancy or your child's growth and
development, talk with your doctor.
Causes Human cells
normally contain 23 pairs of chromosomes. One chromosome in each pair comes
from your father, the other from your mother. Down syndrome results when
abnormal cell division involving chromosome 21 occurs. These cell division
abnormalities result in an extra partial or full chromosome 21. This extra
genetic material is responsible for the characteristic features and
developmental problems of Down syndrome.
Any one of three genetic
variations can cause Down syndrome: Trisomy 21. About 95 percent of the
time, Down syndrome is caused by trisomy 21 — the person has three copies of
chromosome 21, instead of the usual two copies, in all cells. This is caused by
abnormal cell division during the development of the sperm cell or the egg
cell. Mosaic Down syndrome. In this rare form of Down syndrome, a person has
only some cells with an extra copy of chromosome 21. This mosaic of normal and
abnormal cells is caused by abnormal cell division after fertilization.
Translocation Down syndrome. Down syndrome can also occur when a portion of
chromosome 21 becomes attached (translocated) onto another chromosome, before
or at conception. These children have the usual two copies of chromosome 21,
but they also have additional genetic material from chromosome 21 attached to
another chromosome. There are no known behavioral or environmental factors that
cause Down syndrome.
Is it inherited? Most of
the time, Down syndrome isn't inherited. It's caused by a mistake in cell
division during early development of the fetus. Translocation Down syndrome can
be passed from parent to child. However, only about 3 to 4 percent of children
with Down syndrome have translocation and only some of them inherited it from
one of their parents. When balanced translocations are inherited, the mother or
father has some rearranged genetic material from chromosome 21 on another
chromosome, but no extra genetic material. This means he or she has no signs or
symptoms of Down syndrome, but can pass an unbalanced translocation on to
children, causing Down syndrome in the children.
Risk factors Some parents
have a greater risk of having a baby with Down syndrome. Risk factors include:
Advancing maternal age. A woman's chances of giving birth to a child with Down
syndrome increase with age because older eggs have a greater risk of improper
chromosome division. A woman's risk of conceiving a child with Down syndrome
increases after 35 years of age. However, most children with Down syndrome are
born to women under age 35 because younger women have far more babies. Being
carriers of the genetic translocation for Down syndrome. Both men and women can
pass the genetic translocation for Down syndrome on to their children. Having
had one child with Down syndrome. Parents who have one child with Down syndrome
and parents who have a translocation themselves are at an increased risk of
having another child with Down syndrome. A genetic counselor can help parents
assess the risk of having a second child with Down syndrome.
Complications People with
Down syndrome can have a variety of complications, some of which become more
prominent as they get older. These complications can include: Heart defects.
About half the children with Down syndrome are born with some type of
congenital heart defect. These heart problems can be life-threatening and may
require surgery in early infancy. Gastrointestinal (GI) defects. GI
abnormalities occur in some children with Down syndrome and may include
abnormalities of the intestines, esophagus, trachea and anus. The risk of
developing digestive problems, such as GI blockage, heartburn (gastroesophageal
reflux) or celiac disease, may be increased. Immune disorders. Because of
abnormalities in their immune systems, people with Down syndrome are at
increased risk of developing autoimmune disorders, some forms of cancer, and
infectious diseases, such as pneumonia. Sleep apnea. Because of soft tissue and
skeletal changes that lead to the obstruction of their airways, children and
adults with Down syndrome are at greater risk of obstructive sleep apnea.
Obesity. People with Down syndrome have a greater tendency to be obese compared
with the general population. Spinal problems. Some people with Down syndrome
may have a misalignment of the top two vertebrae in the neck (atlantoaxial
instability). This condition puts them at risk of serious injury to the spinal
cord from overextension of the neck. Leukemia. Young children with Down
syndrome have an increased risk of leukemia. Dementia. People with Down
syndrome have a greatly increased risk of dementia — signs and symptoms may
begin around age 50. Having Down syndrome also increases the risk of developing
Alzheimer's disease. Other problems. Down syndrome may also be associated with
other health conditions, including endocrine problems, dental problems,
seizures, ear infections, and hearing and vision problems. For people with Down
syndrome, getting routine medical care and treating issues when needed can help
with maintaining a healthy lifestyle.
Life expectancy Life spans
have increased dramatically for people with Down syndrome. Today, someone with
Down syndrome can expect to live more than 60 years, depending on the severity
of health problems.
Prevention There's no way
to prevent Down syndrome. If you're at high risk of having a child with Down
syndrome or you already have one child with Down syndrome, you may want to
consult a genetic counselor before becoming pregnant. A genetic counselor can
help you understand your chances of having a child with Down syndrome. He or
she can also explain the prenatal tests that are available and help explain the
pros and cons of testing.
Diagnosis The American
College of Obstetricians and Gynecologists recommends offering the option of
screening tests and diagnostic tests for Down syndrome to all pregnant women,
regardless of age. Screening tests can indicate the likelihood or chances that
a mother is carrying a baby with Down syndrome. But these tests can't tell for
sure or diagnose whether the baby has Down syndrome. Diagnostic tests can
identify or diagnose whether your baby has Down syndrome. Your health care
provider can discuss the types of tests, advantages and disadvantages, benefits
and risks, and the meaning of your results. If appropriate, your provider may
recommend that you talk to a genetics counselor.
Screening tests during
pregnancy Screening for Down syndrome is offered as a routine part of
prenatal care. Although screening tests can only identify your risk of carrying
a baby with Down syndrome, they can help you make decisions about more-specific
diagnostic tests. Screening tests include the first trimester combined test and
the integrated screening test. The first trimester combined test The first
trimester combined test, which is done in two steps, includes: Blood test. This
blood test measures the levels of pregnancy-associated plasma protein-A
(PAPP-A) and the pregnancy hormone known as human chorionic gonadotropin (HCG).
Abnormal levels of PAPP-A and HCG may indicate a problem with the baby. Nuchal
translucency test. During this test, an ultrasound is used to measure a specific
area on the back of your baby's neck. This is known as a nuchal translucency
screening test. When abnormalities are present, more fluid than usual tends to
collect in this neck tissue. Using your age and the results of the blood test
and the ultrasound, your doctor or genetic counselor can estimate your risk of
having a baby with Down syndrome. Integrated screening test The integrated
screening test is done in two parts during the first and second trimesters of
pregnancy. The results are combined to estimate the risk that your baby has
Down syndrome. First trimester. Part one includes a blood test to measure
PAPP-A and an ultrasound to measure nuchal translucency. Second trimester. The
quad screen measures your blood level of four pregnancy-associated substances:
alpha fetoprotein, estriol, HCG and inhibin A.
Diagnostic tests during
pregnancy If your screening test results are positive or worrisome, or
you're at high risk of having a baby with Down syndrome, you might consider
more testing to confirm the diagnosis. Your health care provider can help you
weigh the pros and cons of these tests. Diagnostic tests that can identify Down
syndrome include: Chorionic villus sampling (CVS). In CVS, cells are taken from
the placenta and used to analyze the fetal chromosomes. This test is typically
performed in the first trimester, between 10 and 13 weeks of pregnancy. The
risk of pregnancy loss (miscarriage) from a CVS is very low. Amniocentesis. A
sample of the amniotic fluid surrounding the fetus is withdrawn through a
needle inserted into the mother's uterus. This sample is then used to analyze
the chromosomes of the fetus. Doctors usually perform this test in the second
trimester, after 15 weeks of pregnancy. This test also carries a very low risk
of miscarriage. Preimplantation genetic diagnosis is an option for couples
undergoing in vitro fertilization who are at increased risk of passing along
certain genetic conditions. The embryo is tested for genetic abnormalities
before it's implanted in the womb.
Diagnostic tests for newborns
After birth, the initial diagnosis of Down syndrome is often based on the
baby's appearance. But the features associated with Down syndrome can be found
in babies without Down syndrome, so your health care provider will likely order
a test called a chromosomal karyotype to confirm diagnosis. Using a sample of
blood, this test analyzes your child's chromosomes. If there's an extra
chromosome 21 in all or some cells, the diagnosis is Down syndrome.
Treatment Early
intervention for infants and children with Down syndrome can make a major
difference in improving their quality of life. Because each child with Down
syndrome is unique, treatment will depend on individual needs. Also, different
stages of life may require different services.
Team care If your child
has Down syndrome, you'll likely rely on a team of specialists that can provide
medical care and help him or her develop skills as fully as possible. Depending
on your child's particular needs, your team may include some of these experts: Primary
care pediatrician to coordinate and provide routine childhood care: Pediatric
cardiologist, Pediatric gastroenterologist, Pediatric endocrinologist,
Developmental pediatrician, Pediatric neurologist, Pediatric ear, nose and
throat (ENT) specialist, Pediatric eye doctor (ophthalmologist), Audiologist,
Speech pathologist, Physical therapist, Occupational therapist You'll need to
make important decisions about your child's treatment and education. Build a
team of health care providers, teachers and therapists you trust. These
professionals can help evaluate the resources in your area and explain state
and federal programs for children and adults with disabilities.
Coping and support When
you learn your child has Down syndrome, you may experience a range of emotions,
including anger, fear, worry and sorrow. You may not know what to expect, and
you may worry about your ability to care for a child with a disability. The
best antidote for fear and worry is information and support. Consider these
steps to prepare yourself and to care for your child: Ask your health care
provider about early intervention programs in your area. Available in most
states, these special programs offer infants and young children with Down
syndrome stimulation at an early age (typically until age 3) to help develop
motor, language, social and self-help skills. Learn about educational options
for school. Depending on your child's needs, that may mean attending regular
classes (mainstreaming), special education classes or both. With your health
care team's recommendations, work with the school to understand and choose
appropriate options. Seek out other families who are dealing with the same
issues. Most communities have support groups for parents of children with Down
syndrome. You can also find internet support groups. Family and friends can
also be a source of understanding and support. Participate in social and
leisure activities. Take time for family outings and look in your community for
social activities such as park district programs, sports teams or ballet
classes. Although some adaptations may be required, children and adults with
Down syndrome can enjoy social and leisure activities. Encourage independence. Your
child's abilities may be different from other children's abilities, but with
your support and some practice your child may be able to perform tasks such as
packing lunch, managing hygiene and dressing, and doing light cooking and
laundry. Prepare for the transition to adulthood. Opportunities for living,
working, and social and leisure activities can be explored before your child
leaves school. Community living or group homes, and community employment, day
programs or workshops after high school require some advance planning. Ask
about opportunities and support in your area. Expect a bright future. Most
people with Down syndrome live with their families or independently, go to
mainstream schools, read and write, participate in the community, and have jobs.
People with Down syndrome can live fulfilling lives.
https://www.mayoclinic.org/diseases-conditions/down-syndrome/diagnosis-treatment/drc-20355983
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