Down's Syndrome

Patient Education

Introduction

Down syndrome (DS) is a genetic disorder caused by the presence of all or part of the third copy of chromosome 21. It is typically associated with physical growth delays, characteristic facial features, and mild to moderate intellectual disability.

Manifestations and disabilities of Down syndrome

Those with Down syndrome nearly always have physical and intellectual disabilities. As adults, their mental abilities are typically similar to those of an 8- or 9-year-old. They also typically have a poor immune function and generally reach developmental milestones at a later age. They have an increased risk of a number of other health problems, including congenital heart disease, leukemia, thyroid disorders, and mental illness.

Physical characteristics

People with Down syndrome may have some or all of these physical characteristics: a small chin, slanted eyes, poor muscle tone, a flat nasal bridge, a single crease of the palm, and a protruding tongue due to a small mouth and large tongue. Instability of the atlantoaxial joint occurs in about 20% and may lead to spinal cord injury in 1-2%.

Growth in height is slower, resulting in adults who tend to have short stature—the average height for men is 154 cm (5 ft 1 in) and for women is 142 cm (4 ft 8 in). Individuals with Down syndrome are at increased risk for obesity as they age.

Mental subnormality in Down syndrome

Most individuals with Down syndrome have mild (IQ: 50-70) or moderate (IQ: 35-50) intellectual disability with some cases having severe (IQ: 20-35) difficulties.

Many developmental milestones are delayed.

Commonly, individuals with Down syndrome have better language understanding than the ability to speak. They typically do fairly well with social skills.

Behavior problems are not generally as great an issue as in other syndromes associated with intellectual disability. While generally happy, symptoms of depression and anxiety may develop in early adulthood.

Other manifestations

Children and adults with Down syndrome are at increased risk of seizures Many (15%) who live 40 years or longer develop dementia of the Alzheimer's type.

Hearing and vision disorders occur in more than half of people with Down syndrome. Even a mild degree of hearing loss can have negative consequences for speech, language understanding, and academics.

The rate of congenital heart disease in newborns with Down syndrome is around 40%.

Cancers of the blood are 10 to 15 times more common in children with Down syndrome.

Low thyroid hormone levels occur in almost half of all individuals with Down syndrome. This is treatable with oral thyroxine. Constipation also occurs in nearly half of people with Down syndrome and may result in changes in behavior.

Males with Down syndrome usually do not father children, while females have lower rates of fertility relative to those who are unaffected.

Screening

Guidelines recommend screening for Down syndrome to be offered to all pregnant women, regardless of age. If screening is positive, invasive tests like amniocentesis or chorionic villous sampling are required to confirm the diagnosis. Screening in both the first and second trimesters is better than just screening in the first trimester.

Several blood markers can be measured to predict the risk of Down syndrome during the first or second trimester along with ultrasound results.

The diagnosis can often be suspected based on the child's physical appearance at birth. An analysis of the child's chromosomes is needed to confirm the diagnosis, and to determine if a translocation is present, as this may help determine the risk of the child's parents having further children with Down syndrome.

Management

Efforts such as early childhood intervention, screening for common problems, medical treatment where indicated, a good family environment, and work-related training can improve the development of children with Down syndrome. Education and proper care can improve the quality of life. Typical childhood vaccinations are recommended.

Health screening

1. Hearing at 6 months, 12 months, then yearly and in adults every 3-5 years
2. Thyroid test at 6 months, then yearly
3. Eyes at 6 months, then yearly
4. Dental check-up at 2 years, then yearly
5. Neck X-rays - Between 3 and 5 years of age
6. Heart - electrocardiogram and ultrasound of the heart at birth.

Surgical repair of heart problems may be required as early as three months of age.

Cognitive development

Hearing aids or other amplification devices can be useful for language learning in those with hearing loss. Speech therapy may be useful and is recommended to be started around 9 months of age. As those with Down's typically have good hand-eye coordination, learning sign language may be possible. Education programs before reaching school age may be useful. School-age children with Down syndrome may benefit from inclusive education (whereby students of differing abilities are placed in classes with their peers of the same age), provided some adjustments are made to the curriculum.

Outlook

Although many Down syndrome children have physical and mental limitations, they can live independent and productive lives well into adulthood. The level of intellectual disability varies but is usually moderate. Adults with Down syndrome have an increased risk of dementia.

Severe heart problems or certain types of leukemia can cause early death in patients with Down syndrome.

Prevention

A woman's risk of having a child with Down syndrome increases as she gets older. The risk is significantly higher among women age 35 and older. Hence, all pregnant women, especially those older than 35 years should be screened for Down syndrome in the baby.

Couples who already have a baby with Down syndrome have an increased risk of having another baby with the condition and need genetic counseling. Tests can be done on a fetus during the first few months of pregnancy to check for Down syndrome.