Signs of Down syndrome usually appear at birth or shortly thereafter. Many children with the condition have a flat face, small ears and mouth, and broad hands and feet, although these features vary from person to person. Most young children have a lack of muscle tone (hypotonia), which generally improves by late childhood.
Often developmental disabilities result from the combination of a lower intelligence level and physical limitations related to Down syndrome. Heart defects, intestinal abnormalities, and irregular ear and respiratory tract structures can also occur and cause additional symptoms or lead to complications.