Cian McDonnell-Lynch suffers from a one-in-a-million disorder. His family has traveled to Boston to save his life with a lung transplant.Hope for Cian / Facebook

Four-year-old Irish boy Cian McDonnell-Lynch, who suffers from a one-in-a-million disorder, has been told by doctors that he has just a few months to live.

His distraught family is now in the US, consulting with Boston Children’s Hospital on whether he will be able to undergo a life-saving lung transplant operation.

Because the procedure will not be covered by their Irish health insurance, the McDonnell-Lynches have launched an online campaign to raise the $1 million needed to cover the transplant surgery and young Cian’s recovery costs.

Cian was born with Dyskeratosis Congenita, a rare bone marrow disorder. “It affects one in a million. And Cian is actually at the more severe end of the syndrome,” his mother, Lisa McDonnell, explained in an interview with the Boston station WBZ-TV.

He lost his eyesight when he was just one year old, and shortly after that his bone marrow began failing. Cian’s condition is so rare that reaching a diagnosis took many months as his condition deteriorated.

He had a successful bone marrow transplant in March 2013, giving his family hope, but then tragedy struck again at the start of this year when he began experiencing low energy and blood oxygen saturation. Weeks of testing revealed that another rare and serious disorder, microscopic pulmonary AVMS, is now affecting his lungs.

His only hope now is a lung transplant, but because he is so young and his disorder is so uncommon, hospitals in Ireland and the UK told his parents they wouldn’t be able to perform the surgery.

“He was the first child that they’ve seen with this condition,” Lisa told WBZ-TV. “It’s just so rare. I think they’re just afraid of what the outcome is going to be; his quality of life afterwards. But we just can’t give up on him.”

Without the transplant it’s unlikely that Cian will live past Christmas, doctors have said.

Cian just finished his fourth day of tests at Boston Children’s Hospital to see whether he will be deemed suitable to go on the list for a lung transplant.

Day 4 of the assessment in Boston Childrens Hospital. It's tough going but hopefully it will all be worthwhile in the...

Posted by Hope for Cian on Thursday, August 27, 2015

His parents and sister are all by his side and remaining hopeful. The GoFundMe account they set up to raise money for the surgery has taken off as Cian’s story spreads around the world, from Ireland to the US to Australia. So far close to 5,000 people have raised nearly €125,000 ($140,000). The McConnell-Lynches are asking for donations as small as €10, and for each person who donates to tell 10 more people about Cian’s journey.

Donations can be made vie the GoFundMe page. To stay up to date on Cian’s progress, you can visit the Hope for Cian Facebook or website.