Down syndrome results from this extra genetic material. Scientists are still learning about what causes this extra genetic material and exactly how it causes the problems of Down syndrome. Down syndrome is the most common disorder of human chromosomes. It is usually diagnosed shortly after birth during a baby's first physical exam. The diagnosis is usually based on physical characteristics of the syndrome.
Eyes often have a slant to the openings and extra skin at the middle corner.
The mouth tends to stay open with the tongue sticking out. Muscle tone is usually low, making the arms and legs more relaxed. Growth and development is unique to every child. Children learn to walk, run, use their hands and eyes, understand language, speak, think, and solve problems at different rates. Children with Down syndrome, like all children, do all of these things too.