But what terrifies Gabby's parents the most is the fear that she could make herself blind. Trish recalled the time Gabby turned 1 year old.
"She woke up from a nap, and I thought, 'Oh, there's a little bit of fuzz or fluff in her eye,'" Trish said. "It wasn't fuzz, there was a real mark on her cornea. So I quickly called the local doctor, and he said, 'If you had this, you would be in such excruciating pain you couldn't open your eye.'"
Gabby's left eye was so badly damaged that her doctor stitched her eyelid shut in a desperate bid to save her vision. But because Gabby didn't feel the pain of it, she ripped her own stitches out.
Then Steve came up with the idea of using swim goggles to protect Gabby's eyes. But it was already too late. She had lost the vision in her left eye. And now it was at risk of developing into a life-threatening infection.
The only solution was to remove the injured eye.
"It just brings back those images of the hospital, and letting her go on the gurney, and, and now it's — No parent should ever have to watch her child do that," Trish said.
"I remember it being an easy decision that we needed to take the eye out — but it was, we weren't fixing anything. It was taking something away."
Today Gabby has an artificial left eye. She wears a protective contact lens over the right one, which is also damaged. For good measure, she uses safety glasses during the day — and those swim goggles at night.
Despite these precautions, she still manages to hurt herself constantly. Gabby told "Primetime" that she had once broken her jaw without even knowing, because it didn't hurt.
Experts aren't sure whether kids like Gabby can reach adulthood or have normal lives.
But Joann Cruz might be a glimpse into Gabby's future. Cruz, 37, has also never felt pain. The damage she has accidentally done to her body is mind-boggling. But most impressive of all is her determination to live as normally as possible.
"My parents, especially my mom, always told me, 'There's nothing different about you. You're a regular person.' And I always believed that," Cruz said.
Cruz added she doesn't know what pain feels like. Millions of Americans suffer from back pain, but Joann has repeatedly damaged the discs in her spine and never known it. She's had six major back surgeries and a rod inserted to hold her vertebrae together.
"This last one that I had last year, I broke the rod. They had inserted a rod, and I broke it, and I didn't know I broke it," Cruz said. "The only reason I knew I broke it was because as I walked, I could hear it. You could hear it, crack, crack, crack. And I started slouch — slumping over. So if you were standing behind me, you could see the actual broken rod in my back — and my doctor said that only I could do something like that."
Joann's whole life has been filled with unimaginable injuries. The wounds began appearing when she was very young. When teething she bit herself, gouging her lip so badly the damage is still present.
Like Gabby, Joann also had all her baby teeth pulled — and later needed surgery to allow her adult teeth to grow in properly.
For Joann, even simple things can hold untold peril — like knowing when the water gets too hot. Even if it is scalding, she doesn't experience pain.