NORTH TEXAS (CBSDFW.COM) – A North Texas family is running out of time to find a cure for their sons’ rare illness.

The Woleben family celebrates Christmas as they are grateful to still have their son.

Every day, seven-year-old Will Woleben continues to defy the odds.

His father, Doug, said his son’s recent birthday was a milestone.

“The lifespan for this disease is 2 and a half years,” said Doug. “So the fact that Will has made it to seven is already a miracle.”

Will has a neurodegenerative disease called Leigh’s Syndrome.

“It’s creating areas of dead cells in his brain,” said Doug. “As his cells grow larger, we can see his abilities diminish.”

It’s extremely rare, and so far incurable.

Will’s health is fragile, yet, his parents put up a sign outside his room asking visitors to cover their shoes and wash their hands. Even the common cold could land him in the hospital.

Will has lost his ability to speak and eat on his own, but not to play hockey and goal tend.

A team of experts at UT Southwestern are developing a new gene therapy treatment; however, it comes at a cost.

“It’s incredibly expensive to develop this medication and to get to a point where it’s at a human clinical trial,” said Doug. “That’s 3.5 million total to get to that point.”

The gene therapy is in pre-clinical studies now.

“It makes you realize how short life is, and how to cherish all the moments, the small moments, bc you never know when you’re going to lose him,” said Kasey, Will’s mother.

For the parents, each smile and holiday like Christmas with their son is something special to hold onto.

“His ability to connect with everyone around him has not been impacted by this disease,” said Doug. “It’s the important part that we still have. and we’re trying desperately to save that.”

Will’s parents have raised half a million dollars so far with the help of family and the community.

To donate, click here.