"I was massaging Gabby's gums one day, and she bit down on me ungodly hard. It was so hard, I couldn't stand it," Gabby's father, Steve Gingras, told ABC News' Primetime. "When I pulled my finger out, I pulled a tooth out of her mouth -- and she's just happy playing like nothing happened."
Gabby's lack of pain sensation eventually led to the loss of all of her teeth. A badly scratched cornea forced doctors to remove her left eye, and she now wears a helmet and goggles every day to protect herself from serious injury.
In Gabby's case, the condition arose from a genetic accident that stunted the development of nerve fibers crucial in the detection of pain and temperature.
As children with this condition get older, the hazards associated with never knowing the sensation of pain persist. However, a number of people have lived into adulthood with the condition.
Gabby's parents have started a foundation called Gift of Pain, a support group for people with HSAN. So far they have found 39 people who think they have the condition.
"I don't want another mother to ever sit where Steve and I sat five or six years ago and say, 'What is going on? Why can't I get help? Why can't I get information?'" Trish Gingras, Gabby's mother, told "Primetime." "That's really what motivates me."
ABC News' Radha Chitale contributed to this report.