Down syndrome, SIHN drohm, formerly called Mongolism, is a disorder that is present at birth. It is characterized by mental retardation and such physical features as upward-slanting eyes; a flat nose; a small head; and short, stubby hands. In addition, the ears and teeth are small and abnormally shaped. Down syndrome may be accompanied by heart disorders, poor vision, and respiratory problems. The degree of mental retardation in children ranges from severe to mild.