This is what happens for persons who have what is diagnosed as "down syndrome". It is because the person has too MUCH genetic information.
Some of the symptoms of Down Syndrome, or Trisomy 21 are:
-wide range of mental abilities
-round, full face
-enlarged and creased tongue
Joe: "Did you hear about the new kid? He has down syndrome! Poor guy!"
Bob: "We learnt about that in Bio class!"
Joe: "Your mama is sooo fat..."
Bob: "Oh ya?! Well, you have Trisomy 21!"