• Decreased muscle tone at birth
• Separated sutures (joints between the bones of the skull)
• Asymmetrical or odd-shaped skull
  • Round head with flat area at the back of the head (occiput)
  • Small skull (microcephaly)
• Upward slanting eyes, unusual for ethnic group
• Small mouth with protruding tongue (see tongue problems)
• Broad short hands
• Single crease on the palm
• Retarded growth and development
• Delayed mental and social skills (mental retardation)
• Iris lesion (an abnormality of the colored part of the eye called Brushfield spots)

A heart murmur may be revealed by listening to the chest with a stethoscope. Characteristic abnormalities are revealed by a physical examination. These include a flattened facial profile, small ears, separation of the abdominal muscles, joint hyperflexibility, awkward gait, extra skin on back of neck at birth, and an abnormal bone in the middle of the 5th finger.

Early and massive vomiting may indicate obstruction of the esophagus or duodenum and less often lower segments of the gastrointestinal tract. This is sometimes discovered by inability at birth to pass a tube from the nose into the stomach or duodenum as well as by special x-rays.

Tests include:

• Chromosome studies (demonstrates three copies of 21st chromosome in 94% of cases)
• Chest x-ray (to determine presence of cardiac abnormalities)
• Echocardiogram (to determine nature of cardiac abnormality)
• ECG
• Gastrointestinal x-ray (to show obstruction if symptoms are suggestive)