3 year old Gabby Gingras was born incapable of feeling pain - the rare disease prevents the nerve fibers in her body from being able to pick up and transmit pain signals.
No other cases like it have been found in the US - doctors can only find twelve instances of the disease in the entire world.
Without pain, she can't tell when she is harming herself. As a result, she currently has no teeth, and may have to have one of her eyes removed from complications caused by self injuries when she was an infant.
This is the short version, entire story and more information: Source