Little Forest Lebrocq is in the fight of his life.

After being diagnosed with a rare disease his parents thought was a common cold, the plucky two-year-old from Kuranda, in Far North Queensland, is facing a delicate operation doctors fear he may not survive.

But Forest has proved them wrong before, beating slim odds after emergency heart surgery in Brisbane in July.

"We've been told he is the only case like it in Australia, and medically speaking, he shouldn't be here, but he's a battler," father Shane Lebrocq, 44, said.

Forest has pulmonary vein stenosis, where veins to the heart narrow or become blocked.

The potentially fatal condition was diagnosed in June after Forest endured repeated hospitalisations for colds, a regular complication of the disease which otherwise can show no symptoms until it is very advanced.

"He was always getting a runny nose, and just overnight would go downhill and end up in the ICU," Mr Lebrocq said.

"By the time he was diagnosed, three of the four veins carrying oxygen to the heart from the lungs had failed and shrivelled.

"Doctors at the (Queensland) Children's Hospital operated on his last vein, to widen it, but told us he mightn't make it through the night.

"Well he did, and it was the first time in months we'd seen real colour in his face."

Forest's mother Fay Barton urged other parents to get their children checked for the usually congenital disease, which can also be characterised by fast breathing and fatigue.

"Don't be afraid, you know your child, so if something's not right, keep seeking answers," Ms Barton, 32, said.

She said her son had become a favourite with hospital staff.

"Everyone he meets, he touches them.

"After his surgery he rubbed his chest and said to the surgeon, 'thank you, doctor, I feel better, can I have a kissy now'?

"And the nurses all want to take him home with them, he's such a dear little boy."

The couple, who run a gardening and cleaning business after ditching careers in hospitality, have spent tens of thousands of dollars on Forest's treatment.

"We've done our best to suck it up," Mr Lebrocq said, "but we just don't know what's ahead."

In recent weeks, Forest's condition has flared again and on Monday the pair, also parents to 20-month-old daughter Raign who is "in perfect health", will learn if more high-risk surgery is recommended.

They have started a GoFundMe page to assist with ongoing costs.

Originally published as Toddler battles deadly rare disease mistaken for a cold