Down syndrome is the most common genetic condition. One in every 733 babies is born with Down syndrome. The most common form of Down syndrome is called Trisomy 21, because it involves an extra copy of the 21st chromosome.
Individuals with Down syndrome are becoming increasingly integrated into society and community organizations, such as school, health care systems, work forces, and social and recreational activities. Individuals with Down syndrome possess varying degrees of intellectual disabilities, from very mild to severe. Most people with Down syndrome have IQs in the mild to moderate range of intellectual disability.
Due to advances in medical technology, individuals with Down syndrome are living longer than ever before. In 1910, children with Down syndrome were expected to survive to age nine. With the discovery of antibiotics, the average survival age increased to 19 or 20. Now, with recent advancements in clinical treatment, most particularly corrective heart surgeries, as many as 80% of adults with Down syndrome reach age 60, and many live even longer.
In the United States, approximately 400,000 families have a child with Down syndrome, and about 5,000 babies with Down syndrome are born each year. More and more Americans will interact with individuals with this genetic condition, increasing the need for widespread public education and acceptance.
The additional copy of the 21st chromosome which causes Down syndrome can originate from either the father or the mother. Approximately 5% of the cases have been traced to the father.
Down syndrome can occur in people of all races and economic levels. Older women have an increased chance of having a child with Down syndrome. A 35-year-old woman has about a one in 350 chance of conceiving a child with Down syndrome, and this chance increases gradually to one in 100 by age 40. At age 45 the incidence becomes approximately one in 30.
Since many couples are postponing parenting until later in life, the incidence of Down syndrome conceptions is expected to increase. Therefore, genetic counseling for parents is becoming increasingly important. Still, many physicians are not fully informed about advising their patients about the incidences of Down syndrome, advancements in diagnosis, and the protocols for care and treatment of babies born with Down syndrome.
Down syndrome is a developmental condition. As researchers learn more about the molecular genetics and other aspects of Down syndrome, they also obtain valuable information about human development and can advance the study of many biological processes.
In addition, individuals with Down syndrome have a higher incidence of certain medical conditions, and the study of Down syndrome may yield important breakthroughs in those areas. Research in Down syndrome provides a way for looking at many important problems:
Heart disease: Up to 50% of individuals with Down syndrome are born with congenital heart conditions. The majority of heart conditions in children with Down syndrome can now be surgically corrected with resulting long-term health improvements. However, scientists continue to search for the cause of these heart conditions and look for means of prevention.
Alzheimer’s disease: Estimates vary, but it is reasonable to conclude that 25% or more of individuals with Down syndrome over the age of 35 will develop the clinical signs and symptoms of Alzheimer’s-type dementia.
Leukemia: Approximately one in every 100 individuals with Down syndrome will develop leukemia; or, to put it another way, 99% of people with Down syndrome will not develop leukemia. The majority of cases are categorized as acute megakaryoblastic leukemia, which tends to occur in the first three years of life, and for which there is a high cure rate. A transient form of leukemia is also seen in newborns with Down syndrome, disappearing spontaneously during the first two to three months of life.
People with Down syndrome also have specific health care needs, above and beyond standard medical care. Additionally, children with Down syndrome grow and develop at different rate than their typical peers. This section also includes health care guidelines, growth charts, and information about specialty clinics, specific to people with Down syndrome.
Down Syndrome Health Care Guidelines follow and individual’s development from birth through adulthood and provide information about potential health concerns at each stage. They are compiled by the Down Syndrome Medical Interest Group, a national affiliation of health care providers who specialize in caring for individuals with Down syndrome. More information on medical guidelines and associated medical conditions is available from the National Down Syndrome Society.