Down syndrome

 

Down syndrome (DS or DNS)

Summary / Definiton 

Down syndrome (DS or DNS), also known as trisomy 21, is a genetic disorder caused by the presence of all, or part of a third copy of chromosome 21. It is typically associated with physical growth delays, characteristic facial features, and mild to moderate intellectual disability. The average IQ of a young adult with Down syndrome is 50, equivalent to the mental age of an 8- or 9-year-old child, but this can vary widely.

Sign & Symptoms

Most children with Down syndrome have:

• Distinctive facial features, such as a flat face, small ears, slanting eyes, and a small mouth.
• A short neck and short arms and legs.
• Low muscle tone and loose joints. Muscle tone usually improves by late childhood.
• Below-average intelligence.
• Many children with Down syndrome are also born with heart, intestine, ear, or breathing problems. These health conditions often lead to other problems, such as airway (respiratory) infections or hearing loss. But most of these problems can be treated.

Causes

Down syndrome is caused by a problem with a baby's chromosomes. Normally, a person has 46 chromosomes. But most people with Down syndrome have 47 chromosomes. In rare cases, other chromosome problems cause Down syndrome. Having extra or abnormal chromosomes changes the way the brain and body develop.
Experts don't know the exact cause, but some things increase the chance that you'll have a baby with Down syndrome. These things are called risk factors.

Your risk of having a baby with Down syndrome is higher if:

• You are older when you get pregnant. Many doctors believe that the risk increases for women age 35 and older.
• You have a brother or sister who has Down syndrome.
• You had another baby with Down syndrome.
• If you've had a baby with Down syndrome and are planning another pregnancy, you may want to talk to your doctor about genetic counseling

Diagnosis

Your doctor may suggest that you have tests during pregnancy to find out if your baby has Down syndrome. You may decide to have:

• Screening tests, such as an ultrasound or a blood test during your first or second trimester. These can help show if the developing baby (fetus) is at risk for Down syndrome. But these tests sometimes give false-positive or false-negative results.
• Diagnostic tests, such as chorionic villus sampling or amniocentesis. These can show if a baby has Down syndrome. You may want to have these tests if you have abnormal results from a screening test or if you are worried about Down syndrome.

Sometimes a baby is diagnosed after birth. A doctor may have a good idea that a baby has Down syndrome based on the way the baby looks and the results of a physical exam. To make sure, the baby's blood will be tested. It may take 2 to 3 weeks to get the test results.

Complications

Children with Down syndrome can have a variety of complications, some of which become more prominent as they get older, such as:

• Heart defects. About half the children with Down syndrome are born with some type of heart defect. These heart problems can be life-threatening and may require surgery in early infancy.
• Leukemia. Young children with Down syndrome have an increased risk of leukemia.
• Infectious diseases. Because of abnormalities in their immune systems, those with Down syndrome are much more at risk of infectious diseases, such as pneumonia.
• Dementia. People with Down syndrome have a greatly increased risk of dementia — signs and symptoms may begin around age 50. Those who have dementia also have a higher rate of seizures. Having Down syndrome also increases the risk of developing Alzheimer's disease.
• 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.
• Other problems. Down syndrome may also be associated with other health conditions, including gastrointestinal blockage, thyroid problems, early menopause, seizures, ear infections, hearing loss, skin problems such as psoriasis, skeletal problems and poor vision.

Life expectancy
Life spans have increased dramatically for people with Down syndrome. In 1910, a baby born with Down syndrome often didn't live to age 10. Today, someone with Down syndrome can expect to live to age 60 and beyond, depending on the severity of health problems.

Treatment

Early intervention for infants and children with Down syndrome can make a major difference in realizing their potential abilities and in their quality of life.
Early intervention programs
Ask your health care provider about early intervention programs in your area. Available in most states, these special programs offer children with Down syndrome stimulation at an early age with appropriate sensory, motor and cognitive activities.

Programs may vary, but they usually involve therapists and special educators whose goal is to help your baby develop motor skills, language, social skills and self-help skills.
Team care
If your child has Down syndrome, you'll likely rely on a team of specialists that, depending on your child's particular needs, will provide your child's medical care and help him or her develop skills as fully as possible. 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
• Physical therapist
• Speech pathologist
• Occupational therapist

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.

Prognosis

Between 5 and 15% of children with Down syndrome in Europe attend regular school. Some graduate from high school; however, most do not. Of those with intellectual disability in the United States who attended high school about 40% graduated. Many learn to read and write and some are able to do paid work. In adulthood about 20% in the United States do paid work in some capacity.  In Europe, however, less than 1% have regular jobs. Many are able to live semi-independently, but they often require help with financial, medical, and legal matters. Those with mosaic Down syndrome usually have better outcomes. 

Individuals with Down syndrome have a higher risk of early death than the general population. This is most often from heart problems or infections.  Following improved medical care, particularly for heart and gastrointestinal problems, the life expectancy has increased. This increase has been from 12 years in 1912, to 25 years in the 1980s, to 50 to 60 years in the developed world in the 2000s.  Currently between 4 and 12% die in the first year of life. The probability of long-term survival is partly determined by the presence of heart problems. In those with congenital heart problems 60% survive to 10 years and 50% survive to 30 years of age. In those without heart problems 85% survive to 10 years and 80% survive to 30 years of age. About 10% live to 70 years of age. The National Down Syndrome Society have developed information regarding the positive aspects of life with Down syndrome. 

Epidemiology

Globally, as of 2010, Down syndrome occurs in about 1 per 1000 births and results in about 17,000 deaths. More children are born with Down syndrome in countries where abortion is not allowed and in countries where pregnancy more commonly occurs at a later age. About 1.4 per 1000 live births in the United States and 1.1 per 1000 live births in Norway are affected. In the 1950s, in the United States, it occurred in 2 per 1000 live births with the decrease since then due to prenatal screening and abortions. The number of pregnancies with Down syndrome is more than two times greater with many spontaneously aborting. It is the cause of 8% of all congenital disorders. 

Maternal age affects the chances of having a pregnancy with Down syndrome. At age 20, the chance is one in 1441; at age 30, it is one in 959; at age 40, it is one in 84; and at age 50 it is one in 44. Although the probability increases with maternal age, 70% of children with Down syndrome are born to women 35 years of age and younger, because younger people have more children. The father's older age is also a risk factor in women older than 35, but not in women younger than 35, and may partly explain the increase in risk as women age.