When Glenn and Cara O'Neill found out their daughter Eliza had a rare metabolic disorder known as Sanfilippo syndrome, they swore their family would do whatever they could to save her life.

Fast forward two years, and the family has just finished two years of living in isolation.

Yes. For 726 days, Glenn and Cara, along with Eliza and their other child, Beckham, lived completely isolated from family, friends and the outside world.

Eliza, now six years old, was diagnosed with Sanfilippo syndrome as a baby. Two years ago, there was a chance she would be a suitable candidate for a never-before-tried clinical trial to treat the condition. But in order for her to qualify for consideration, the family had to go into isolation.

For Glenn and Cara, it wasn't even a question. They were willing to do whatever it took. Their decision, unimaginable for many us, is a testament to a parent's love for their child.

"It was very difficult. We had no way of knowing when the trial would start, and when it did, if she would be picked," Glenn told Redbookmag.com.

"The longer it went, the crazier it became. When we originally went into this, we thought that the clinical trial was about six months away. But the road to clinical trials in rare disease has a lot of hurdles, and it never goes as fast as you want when you're the desperate parent of a dying child."

In May this year, the O'Neill family received the news they had been waiting two years for: Eliza was selected as the first person to undergo the new gene therapy treatment. After her first round of treatment, the family's isolation ended.

"We went to the grocery store for the first time in two years and it was so surreal," Glenn says.

"It was like going into the twilight zone, to be around people again. The isolation took a toll on us, but we made it. She got the medicine."

In the four months since, the family have only seen positive changes in Eliza.

"Before the treatment pain, suffering, degeneration, wheelchairs, feeding tubes and, eventually, death were her certain future," Glenn says.

"Now her future is uncertain, and that's an amazing thing."