Nash Jones is the only person in New Zealand Lesch-Nyhan Syndrome - it can result in kidney issues, self-mutilating behavior, disabilities and death at a young age.

When Nathan Jones and Fran Gulliver's son Nash wasn't developing like a normal baby they were told he may have Cerebral Palsy.

Now, they wish he did.

By the time baby Nash reaches 20, his teeth will most likely have been removed to prevent him from biting his fingers off.

ANDY JACKSON/STUFF Nash is surrounded by love from the public and loved ones including his brother Quinn Jones, 2, father Nathan Jones, mother Fran Gulliver, and sister Jess Bielski-Jones, 9.

He could also either be in a wheelchair, or dead.

Lesch-Nyhan Syndrome is caused by a mutation of genes that can result in constant kidney issues, physical and mental disabilities, and potentially bring on self-mutilating behaviours – something no other disease does.

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ANDY JACKSON/STUFF Jones says it breaks them to think their gorgeous wee boy will potentially develop self-mutilating behavior.

Nash's parents, Jones and Gulliver, from New Plymouth, were initially told their baby son might have Cerebral Palsy when he wasn't developing normally.

"We were just sitting at the hospital crying," Jones said. "Then about two weeks later we were up at the hospital, and they were saying it could be this condition called Lesch-Nyhan Syndrome.

"We just googled that, and our world fell down around us. It was like holy; we're actually hoping that it's just Cerebral Palsy."

ANDY JACKSON/STUFF The family enjoys every day they get with wee Nash.

It's been less than 48 hours since Nash was last in hospital. He was passing a kidney stone – seven of which he has already had surgically removed from his left kidney.

The family, including Nash's siblings Jess Bielski-Jones, 9, and Quinn Jones, 2 and a half, is currently in limbo – they spend time in and out of Starship Hospital in Auckland and Taranaki Base Hospital in New Plymouth.

Jones said Lesch-Nyhan Syndrome, which only affects young boys, could mean Nash will try to bite his fingers, tongue and lips off as well as do things like throwing his head against the wall or even gouge his eyes out.

"We're just waiting because the behavioural stuff can start from any time now," he said. "So every time he sticks his tongue out or his lip goes in his mouth, you're just scared that self-harm or self-mutilating behaviour is starting to kick off.

"It's horrible because you know it's coming, it's just a matter of when."

This is the most terrifying part of the syndrome for the family.

"It just breaks you," Jones said. "He's just such a gorgeous little boy at the moment."

The one proven treatment – the worst part for the family – is to remove Nash's teeth. But the family are looking for alternative options.

While rare in New Zealand, Dr Callum Wilson, who specialises in rare diseases, said the condition is known among medical professionals.

"It's a very well-known disease because the clinical picture is so characteristic, and so dramatically awful," Wilson said.

"He'll get developmental regression, so his brain will get destroyed, and he'll have self-mutilating behaviours, and he will die."

Wilson is the founder and clinical director of the national metabolic service based at Starship Hospital.

He said the kidney stones and their cause is relatively easy to treat, but the behavioural side isn't.

"He'll be on some medication but essentially his prognosis is absolutely horrid."

In saying all of this, and knowing that Nash may never walk or talk, the family still have smiles on their faces and are more positive than most.

"You have to be," Jones said. "You've got to be on track; you've still got lives to live and be there for the other kids and still function at work."

Gulliver said the thought of losing Nash breaks their heart.

"We know that he won't be here for that long, so that's a pretty strange reality to come to as parents," she said. "So we just try to enjoy every day."

*The family have a Givealittle page to raise funds for Nash's medical expenses.