Executive summary significant progress has been made in research on down syndrome since the first national institutes of health (nih) research plan on down syndrome was published in october Ò€¦ Down syndrome is a set of cognitive and physical symptoms that result from having an extra chromosome 21 or an extra piece of that chromosome. It is the most common chromosomal cause of Ò€¦

The symptoms of down syndrome vary from person to person, and people with down syndrome may have different problems at different times of their lives.