Down syndrome is caused by the presence of an extra chromosome in the body cells. John Langdon Down the doctor who first described it. Down syndrome is a genetic condition. Different countries use different names for Down syndrome. People with Down syndrome all have a certain degree of learning disability. It means that they are slower to learn new things than other people. The common features of Sown Syndrome are; A lower than average birth weight and shorter than average, Broad hands with short fingers, A small mouth and tongue look a bit too big, looser muscle an joints. The older woman is, the more likely she is to have a baby with Down syndrome.