Down Syndrome occurs when an individual has three rather than two copies of the 21st chromosome. This additional genetic material alters the course of development and causes the characteristics associated with Down Syndrome. A few of the common physical traits of Down Syndrome are low muscle tone, small stature, an upward slant of the eyes and a single crease across the center of the palm. These symptoms of Down Syndrome can range from mild to profound.
This syndrome is the most commonly occurring chromosomal condition, with one in every 733 babies being born with Down Syndrome. People with Down Syndrome have an increased risk for certain medical conditions such as congenital heart defects, respiratory and hearing problems, Alzheimer's disease, childhood leukemia and thyroid conditions. The incidence of births of children with Down Syndrome increases with the age of the mother, however, due to higher fertility rates in younger women, 80 percent of children with Down Syndrome are born to women under 35 years of age.
The most common form of Down Syndrome is known as Trisomy 21. Individuals with Trisomy 21 have 47 chromosomes instead of the usual 46 in each of their cells. There are also two other genetic conditions encompassed within Down Syndrome, which are mosaicism and translocation. The least common is mosaicism, which accounts for 1 to 2 percent of all cases. Translocation accounts for 3 to 4 percent.
All people with Down Syndrome experience a cognitive delay. They nearly always exhibit delays in all the developmental areas of gross motor, fine motor, language and social emotional/self help. Early intervention is the single most important key to long-term success with children who have Down Syndrome. The first years of life are a critical time in a child's development. During birth to age 3, children go through the most rapid and developmentally significant changes. Early intervention is a systematic program of therapy, exercises and activities designed to address all the developmental delays. It is important that early intervention services are provided by experienced pediatric occupational, physical and speech therapists.