He was a happy, healthy little boy who loved mucking about in the sandpit with his diggers.
But in nine heartbreaking months, James Swan has become wheelchair-bound, struck down with a condition so rare there isn't even a name for it.
"Now he can't even walk out to the sandpit and play in that any more," dad Graeme said. "He's losing all his strength every day that goes by."
Four-year-old James' brain and nervous system are failing him. Part of his brain is shrinking, and the nerve fibres in his young body are dying.
While the specialists don't know what to call it, they have told the Wellington family that James' mystery condition is likely to take his life – but when, no-one can say for sure.
"There's no treatment or cure, there's no name for what he has," mum Nicola said. "All the testing he's had has ruled out everything that was treatable or had a cure, so now he's in the 'really rare' category.
"It's life-limiting ... every week there's a decrease in his ability and, for us, we don't have a timeline."
The speed of James' decline has been one of the biggest challenges for his parents and two older brothers, Oliver, 6, and Marcus, 8.
In February, the family filmed James dancing. Now he struggles to hold his body up.
"The emotional toll, it's pretty huge on everybody," Nicola said. "It's a bit like riding a rollercoaster, but we keep thinking we're going to be able to get off it and we can't.
"When people tell you you need to start organising a funeral, you know, write it down and put it in the cupboard so that when the day comes, you can just hand it to somebody – what parent is supposed to be able to do that for a 4-year-old?"
The family tries to draw strength from James' bravery.
Recently, he was in agony when medication wore off while he was having a lumbar puncture. He screamed in pain – but once the procedure was complete, he high-fived the medical staff and thanked them for taking the pain away.
However, the cost of his care is having a big impact on their financial affairs.
They have launched a Givealittle page to help fundraise for a mobility van to get James to medical appointments, which costs about around $40,000.
His bedroom in the family's Newlands home will need to be altered to allow a hospital bed to be put in.
When James turns 5 in November, his family will need to pay for his physiotherapy, which will no longer be covered by the taxpayer.
Petrol, hospital parking and shoes big enough to accommodate his splints are among the long list of other costs they have to meet – amounting to about $100,000 all up.
The family are looking forward to taking a trip to Disneyland in June, after winning a competition earlier this year.
"We're just hoping to make magical memories. Lots of photos of all three boys together enjoying themselves without any thought of hospital appointments or therapy," Nicola said.
"James is desperate to go to Mickey Mouse's house. So as long as we see Mickey Mouse, we'll be happy."