The most impossible decision a parent can face.

It’s the dilemma no parent would ever want to face.

What do you do when your child has a rapidly declining degenerative condition? What do you do when your child needs one of only 15 places available in a ground-breaking clinical trial? And what would you do if you had two children with the condition?

Do you tell other sufferers to apply for the trial, while knowing in your heart every new applicant reduces your own child’s chances of being picked?

Do you continue fundraising the millions needed to be in the trial, despite knowing the odds of your child being selected against such fierce competition is highly unlikely?

Do you nominate one of your children with the condition, over your other child, to give one a better chance at survival?

Could you?

For most, it seems like an impossible hypothetical. Yet for one family in Australia, this is a reality.

Megan and Allan Donnel have two children – Isla who is five years old and Jude who is three. Both children are suffering from ‘Sanfilippo syndrome‘.

Sanfilippo is a degenerative condition that affects approximately one in every 70,000 births. Though children with the syndrome are born in seemingly perfect health, over time clear delays in advancement begin to appear. For the Donnell’s this was when their daughter, Isla, was 4. The second blow came when a month later they were told younger son Jude had also inherited the condition.

There’s currently no cure for Sanfilippo disease and that means the prognosis for sufferers is “steady mental decline and, ultimately, a young and painful death.” Most patients with Sanfilippo don’t live past their teenage years.

“I just couldn’t believe it. Couldn’t believe that that morning our daughter was slightly delayed, and that evening she was terminally ill,” Megan Donnell said in an interview with 60 Minutes that aired on Sunday night.

“It was almost harder, Jude’s diagnosis, because then we had nothing. Whereas when we thought that Jude was OK, or was going to be OK, we knew that he would be the hope that kept us going. And so I think when we got the diagnosis for him, it was… It just finished us, didn’t it?”

The 60 Minutes report also focused on the story of the O’Neills – a family who have one child with Sanfilippo syndrome. Within weeks of the Donnell’s diagnoses, the O’Neill family from South Carolina, found out their daughter Eliza was met with a similar fate.

Faced with the reality the pharmaceutical companies did not believe such a rare disease was commercially attractive enough to invest in, the families joint together in a global campaign. Megan even quit her job as a management consultant and established the Sanfilippo Children’s Foundation.

This was the video made by the O’Neills to fund the research trial.

The initial aim was to raise $2.5 million to kickstart a clinical trial in the US city of Ohia built upon the work done by the head of biochemical genetics at Adelaide’s Women’s and Children’s Hospital, Professor John Hopwood. He and his team were the first to successfully conduct gene replacement therapy to reduce the symptoms of Sanfilippo in mice.

Now, after tireless videos, bake sales, fundraisers, and campaigns, enough has been raised to begin a human trial in December. The families now have their fingers crossed the next step will be to successfully inject the virus into human Sanfilippo sufferers.

And yet, they remain wary.

Together the Donnells and the O’Neills have raised millions of dollars to support a ground-breaking clinical trial could offer them a glimmer of hope; a chance to have their children’s conditions reversed.

But now, the question remains: how likely is it their children, all Sanfilippo carriers, get three of the 15 places available worldwide in a new clinical trial?

In a cruel twist of fate, these two families who worked so hard to bring the trial to fruition are now up against each other for a spot in the much anticipated trial.

The O’ Neills were asked about what this was like on tonight’s 60 Minutes report:

MICHAEL USHER: You’re doing all of this work, all of this fundraising, not even knowing if Eliza will be accepted into the trial. That’s incredibly tough to deal with.

CARA O’NEILL: Yeah. I mean, what do you do? What do you do?

GLENN O’NEILL: There are new families that that get diagnosed and several have come to us and they say, “Whadda you know in the world, and where’s the research?” and I’m gonna tell them, I’m gonna tell them Ohio and I tell them how great it is and I tell them it’s gene therapy because ethically that’s..I could never not… tell them that… At the same time y- you know your, you know your, y-you know people are, people are… they’ll want the spots, they’re going for.

As for the Donnells? They say it’s unlikely they’ll get two places in the trial.

“Fifteen places worldwide. So we’re realistic that it’s unlikely that we’ll get two of those places,” Megan says.

Though the future is for now uncertain, one thing is clear.  The passion and relentless efforts these families have shown in the face of adversity will result in a cure for Sanfillipos one day. Whether or not their own children will directly benefit from their campaign is yet to be seen.

You can donate to the Australian Sanfilippo Foundation and support their work by going to their website, here.