down syndrome occurs in 1 in 800 live births and their are approximately 350,000 people with down syndrome in the US.
the characteristics (not symptoms) of DS are almond upturned eyes, broader bridge of the nose, brushfiled spots in the eyes (white spots in the iris...looks like the eyes sparkle), shallow pallet, larger tongue, ears are set lower on the head and are generally smaller, thicker fungal fold (back of the neck), shorter stature, simean crease on the palm of the hand (unbroken crease that runs along the width of the inside of the palm), pinkie finger may be bent inward, low muscle tone, congenital heart defects such as av-canal (hole in the chambers of the heart), intestinal blockages, flat feet, sandal toe (wider gap between the big toe and the second toe) lower IQ. (usually between 55-70) prone to Alzheimer's in later years. Now one thing I do want to stress is that these characteristics vary from person to person. some may have quite a few of these characteristic while other may only have a few. their one common trait is that they all have an extra 21st chromosome.
oh...and I just wanted to say too...it isn't a disorder...it is a genetic anomaly.
hope this helps answer your question
mom to a little boy who happens to have down syndrome