In an emotional blog post, a mother to a 3-year-old boy in Ireland has revealed her family's "devastation" after their little one was diagnosed with a rare cancer.

Dublin-based Yavanna Keogh wrote that she and her husband Lar are focussed on spending maximum time with their son Oscar to give him "the time of his life for however long that is".

"There were small signs that something was wrong in the months leading us to here, but they were vague and seemingly disconnected," Keogh, the mind behind Makeupmonster — a popular beauty blog, shared in her post.

After repeated episodes of vomiting around New Year's Eve, Oscar was admitted to the hospital earlier this month, where he was found to be suffering from Diffuse Intrinsic Pontine Glioma (DIPG) — a rare and aggressive type of brain tumour.

"It is incredibly rare, with just 3 or 4 children diagnosed with this every year in Ireland. And somehow it had found Oscar," shared the devastated parent. "It had sat there stealthily growing while we went about our normal lives, making plans, having fun..."

Unfortunately, the tumour is inoperable, and as per Keogh, experimental treatment was not an option for Oscar. "We live in constant fear now," explained the mother-of-one who has no clue when the tumour would turn fatal for her son.

"The median survival for this type of brain tumour is less than a year, with less than 1% of children surviving to 5 years," the blogger mum wrote, adding: "And now Lar and I look ahead wondering if our boy will be with us at Christmas. Will this be the last year we have him here."

While there seems to be no known treatment, the heartbroken parents have started a GoFundMe page to be able to afford radiation therapy, which might help temporarily shrink Oscar's tumour.

Keogh also said that the money raised through the campaign would go towards research and charities based in Ireland. In addition, Oscar's parents have also set up Facebook pages to raise awareness about DIPG considering it is "incredibly rare and brutally underfunded".

"We hope it can be a resource to other families who have dealt with, or are currently dealing with or unfortunately may meet this diagnosis in the future," wrote Keogh.