Down syndrome is a chromosomal disorder that results in the presence of an additional third chromosome 21, also referred to as trisomy 21. Most individuals with Down syndrome have widely recognizable physical characteristics. The severity of Down syndrome ranges from mild to severe. Diagnostic testing for Down syndrome include amniocentesis, chorionic villus sampling, and percutaneous umbilical cord sampling. The most common risk factor for Down syndrome is a woman's age.
Sietske N. Heyn is a medical writer with a PhD in neuroscience. Dr. Heyn's education includes a BS with honors from the University of Oregon, and a doctoral degree in neuroscience from the University of California at Davis. After completing postdoctoral training at the University of California, San Francisco, and many years of working as a medical writer at the Stanford University Center for Down Syndrome Research, Dr. Heyn now runs her own medical writing business.
Dr. Perlstein received his Medical Degree from the University of Cincinnati and then completed his internship and residency in pediatrics at The New York Hospital, Cornell medical Center in New York City. After serving an additional year as Chief Pediatric Resident, he worked as a private practitioner and then was appointed Director of Ambulatory Pediatrics at St. Barnabas Hospital in the Bronx.
Down syndrome (also called Trisomy 21) is a genetic disorder that occurs in
approximately 1 of 830 live births. It is the leading cause of cognitive
impairment. Down syndrome is associated with mild to moderate learning
disabilities, developmental delays, characteristic facial features, and low muscle tone in early infancy. Many individuals with Down syndrome also have heart defects, leukemia, early-onset Alzheimer's disease, gastro-intestinal problems, and other health issues. The symptoms of Down syndrome range from mild to severe.
Life expectancy for individuals with Down syndrome has dramatically increased over the past few decades as medical care and social inclusion have improved. A person with Down syndrome in good health will on average live to age 55 or beyond.
Down syndrome is named after Dr. Langdon Down, who in 1866 first described the syndrome as a disorder. Although Down made some important observations about Down syndrome, he did not correctly identify what causes the disorder. It wasn't until 1959 that scientists discovered the genetic origin of Down syndrome.
Down syndrome is a genetic disorder that is caused by mistakes in cell division during development of the human egg, sperm, or embryo. Over 90% of Down syndrome individuals have three copies of chromosome 21 instead of the normal two in all of their body cells.