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Like other children her age, 4-year-old Eliza O’Neill enjoys singing nursery rhymes, going to the playground and playing with her 7-year-old brother, Beckham.

But unlike most other children her age, Eliza was born with a rare degenerative disease called Sanfilippo Syndrome-Type A.  Because of her condition, Eliza will likely begin experiencing irreversible brain damage by the age of 5 – eventually losing her ability to speak, walk or function normally.

Most children born with Sanfilippo Syndrome-Type A usually die by the time they are teenagers.

Though there are currently no treatments for the disease, researchers at Nationwide Children’s Hospital in Columbus, Ohio have developed a form of gene therapy – successfully tested on mice – that they believe could offer a cure. In an effort to save their daughter’s life, Dr. Cara O’Neill and her husband Glenn, are now fighting to raise $2.5 million to fund a clinical trial for the treatment – before Eliza’s condition worsens.

“It’s hard to imagine that all these things she does today, just like a normal child, are going to go away quickly without this funding,” Glenn O’Neill told FoxNews.com.

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‘There’s nothing we can do’
Eliza was a perfectly normal, healthy 3-year-old girl when her preschool teachers started to observe she was falling slightly behind other children in her class.  They noticed she was having difficulty maintaining conversations, and she struggled to draw with the same accuracy as other kids.

Though not particularly alarmed, Cara, a pediatrician for special needs children, and Glenn took Eliza to a variety of specialists to be evaluated for conditions, including autism spectrum disorders and attention-deficit hyperactivity disorder (ADHD). Eventually, a physician recommended that Eliza undergo genetic testing to rule out a number of conditions.

It was then that the O’Neill family received their shocking diagnosis: Sanfilippo Syndrome-Type A. Seen in just 1 in 70,000 births, Sanfilippo Syndrome causes children to lack an enzyme necessary for normal cellular function.  As a result, Eliza’s disease will eventually cause a lethal build-up of a toxic material called heparan sulfate in her body.

“[Doctors said] there’s no treatment, there’s nothing we can do; go home, enjoy your family,” Cara told FoxNews.com. “…Take home movies, take lots of pictures; record her voice while she still can speak – those kinds of things. We were just stunned.”

Refusing to accept their fate
After the initial shock of Eliza’s diagnosis settled, Glenn and Cara began doing the only thing they could think to help them cope with their grief: research.

“The initial constant crying, once that stopped, we started going about the business of, ‘What are we doing here?’” Cara recalled. “We’re not accepting that there was nothing we could do for her.”

Eventually, Cara came across the work of Dr. Haiyan Fu, of the Center for Gene Therapy at Nationwide Children’s Hospital. Fu had been working on Sanfilippo Syndrome for more than a decade, and she had completed promising research on mice. Using gene therapy, she had successfully rid mice of heparin sulfate build-up, improving their motor skills and allowing them to live a normal life span.

“When I got off the phone [with Fu] I was like, ‘Oh my gosh, this is it Glenn,’” Cara said. “That was the first time I felt a little bit of the weight lifted. We have something to shoot for here; this is real.”

However, the program at Nationwide Children’s Hospital didn’t have the money to fund the manufacturing of the medication – or the funds to run a human clinical trial.

The overall cost of funding both of these services: $2.5 million.

“I didn’t know that in a [rare] disease like this, it’s pretty much left up to the parents [to raise money],” Glenn said. “…What do you do when you’re told you need a couple million for your daughter to even have a chance to live? What do you do when you’re told this?...We made the choice, [and] we’re going to go out, get the word out and not leave anything on the table.”

Saving Eliza
Glenn and Cara got to work.  They created a nonprofit foundation called Cure Sanfilippo Foundation and launched a web site, SavingEliza.com, through the fundraising site GoFundMe.com. Their goal: To raise enough money to allow Nationwide Children’s Hospital to begin manufacturing medication for the trial by June.

As of now, they have amassed about $450,000 – but they have a long way to go, and a short time to fund the trial before Eliza’s condition worsens.

“The really scary thing that frightens us is that we’ve talked with many parents with Sanfilippo [children], and we hear the stories of children doing just as good as Eliza [is now]. But within three to six months, [they] begin to lose speech, start losing their balance,” Glenn said. “You just don’t know when the tipping point is. This disease is working on her every second, building every second. When does that slide down begin? It’s very scary.”

Glenn and Cara have been overwhelmed by the outpouring of support for their cause. Friends, family and strangers have donated to their campaign, and a videographer offered to make a free video that has helped their campaign go viral.

“It would mean absolutely everything to us and for children with this disease [to raise this money],” Glenn said.

To contribute, visit SavingEliza.com.