Down Syndrome (Trisomy 21)

Down syndrome is a genetic condition that causes delays in physical and intellectual development. It occurs in approximately one in every 800 live births. Individuals with Down syndrome have 47 chromosomes instead of the usual 46 due to an extra chromosome 21 (trisomy 21). It is the most frequently occurring chromosomal disorder. The occurrence of Down syndrome is not related to race, nationality, religion or socioeconomic status. Down syndrome is usually caused by an error in cell division called non-disjunction. It is not known why this occurs. However, it is known that the error occurs at conception and is not related to anything the mother did during pregnancy. It has been known for some time that the incidence of Down syndrome increases with advancing maternal age. However, 80% of children with Down syndrome are born to women under 35 years of age.

Down syndrome is usually identified at birth or shortly thereafter. Initially the diagnosis is based on physical characteristics that are commonly seen in babies with Down syndrome. These include low muscle tone, a single crease across the palm of the hand, a slightly flattened facial profile and an upward slant to the eyes. The diagnosis must be confirmed by a chromosome study (karyotype). A karyotype provides a visual display of the chromosomes grouped by their size, number and shape. Chromosomes may be studied by examining blood or tissue cells.

Many children with Down syndrome have health complications beyond the usual childhood illnesses. Approximately 40% of the children have congenital heart defects. It is very important that an echocardiogram be performed on all newborns with Down syndrome in order to identify any serious cardiac problems that might be present. Some of the heart conditions require surgery while others only require careful monitoring. Children with Down syndrome have an increased risk of digestive problems such as include gastroesophageal reflux (a backflow of acidic stomach contents into the esophagus) and celiac disease (an intolerance of a wheat protein called gluten). About 15 percent of people with Down syndrome have hypothyroidism - an underactive thyroid gland. The thyroid gland is a butterfly-shaped organ in the lower neck that produces hormones. Children with Down syndrome also have an increased risk of hearing and vision problems. Additionally, about 1 percent of children with Down syndrome develop cancer of blood-forming cells (leukemia). Adults with Down syndrome have an increased risk of developing Alzheimer disease, a brain disorder that results in a gradual loss of memory, judgment, and ability to function. Although Alzheimer disease is usually a disorder that occurs in older adults, about half of adults with Down syndrome develop this condition by age 50. With appropriate medical care most children and adults with Down syndrome can lead healthy lives. The average life expectancy of individuals with Down syndrome is 60 years, with many living well into their sixties and seventies.

Most children with Down syndrome have mild to moderate impairments but it is important to note that they are more like other children than they are different. Early intervention services should be provided shortly after birth. These services should include physical, speech and developmental therapies. Most children attend their neighborhood schools, some in regular classes and others in special education classes. Some children have more significant needs and require a more specialized program. Some high school graduates with Down syndrome participate in post-secondary education. Many adults with Down syndrome are capable of working in the community, but some require a more structured environment.

Useful Links:

National Down Syndrome Society
(http://www.ndss.org/)

National Association for Down Syndrome
(http://www.nads.org/)

Down Syndrome: Health Issues
(http://www.ds-health.com/)

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