Symptoms. Each person with Down syndrome is an individual â intellectual and developmental problems range from mild to moderate, and some people are healthy while others have severe health problems such as serious heart defects. Children with Down syndrome have a distinct facial appearance. Though not all children with Down syndrome have the same features, some of the more common features are: 1  Flattened facial features. 2  Small head. 3  Short neck. 4  Protruding tongue. 5  Upward slanting eyes, unusual for the child's ethnic group. 6  Unusually shaped or small ears.