Like many toddlers, her brown eyes sparkle when she hears their music and she delights in bopping along to their greatest hits.

But little Isla is not like most two-year-olds.

In fact, she is the only known Australian living with Classic Infantile Batten Disease or CLN1 - a rare and fatal neurological disorder with no known cure.

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The disease will rob Isla of her ability to walk, talk, see and eat. And it will likely claim her life before her sixth birthday.

It's a diagnosis that Isla's parents Nikita and Harley Hunter are still struggling to comprehend.

"Nothing can prepare you for hearing those words," Nikita said, recalling the moment doctors at Melbourne's Royal Children's Hospital delivered the heartbreaking news after months of searching for answers to their daughter's deteriorating health.

"I felt my whole body become numb, like someone had ripped my heart out or shot me point blank. As I searched each one of their faces, desperately waiting to hear our options to save her, we instead heard 'there is no cure' and 'there's nothing we can do'."

But the Hunter family, of Ballarat, which also includes Isla's big brothers Harry, 5, and Paddy, 3, is not giving up on their little girl with Shirley Temple curls and an infectious smile.

They cling to hope that Isla may be a suitable candidate for a clinical trial for gene therapy.

"We are driven by hope that clinical trials for gene therapy will become available to Isla before it's too late," Nikita said.

"In the meantime Harley and I will focus on her beautiful nature and what's truly important in life, which is simply being together."

Dr Ineka Whiteman is the head of research, medical and scientific affairs with Batten Disease Support and Research Association Australia, a not-for-profit organisation dedicated to improving the well-being of patients and families affected by Batten disease.

Dr Whiteman said Batten disease was a complex disorder, with 14 different forms of the disease and more than 400 known gene mutations. It affects one in 100,000 people worldwide.

"Although it's a rare disease there's a lot of research being done around the world. There are a number of companies that are investing in clinical trials to look at basically correcting the faulty gene in these children," she said.

"They basically package up a healthy copy of the gene into a virus and then the virus goes in and overtakes the neurons and transposes the healthy copy of the gene into the nucleus so that that neuron then starts making the healthy version of the gene.

"Because it's working in other forms and they'd be using a very similar viral system in CLN1 there's reason to think that it would also be beneficial for the CLN1 kids."

Dr Whiteman said US-based Abeona Therapeutics and Taysha Gene Therapies had partnered with a goal to run a CLN1 gene therapy clinical trial and was currently going through the FDA approval process.

"This is a perfect candidate for gene therapy," she said.

The Hunter family is committed to raising awareness of Batten disease and hopes that by sharing their story they may help others facing similar battles.

"Before Isla's diagnosis, I'd never heard of it or knew what it was, not even our family doctor had heard of it," Nikita said.

"As parents we were mortified with our daughter's sudden decline. When speaking with paediatricians, a few, well-known "conditions" came to the surface but not one that outlined the whole picture.

"I need to create awareness for her and for this disease, which will eventually take over her mind and body."

Dr Whiteman agreed, saying Batten disease was often misdiagnosed as other disorders including autism, epilepsy and developmental delays.

"Even some of the best neurologists are not familiar with it enough to consider it as a possible diagnosis when they come across a child with all of these collections of unusual symptoms; it's not generally thought of as a first diagnosis," she said.

"One of our objectives as an organisation is to increase education and awareness around that so that we have earlier diagnosis and detection from the clinicians."

A formal register was also critical to advancing awareness and research into the disease, Dr Whiteman said.

For now, they rely on families' self-registering via their website, meaning there could be many cases unknown to them.

"We don't have a formal register in Australia for Batten Disease, which is something that we would love to see more money invested into, more research invested into," she said.

Another goal of the Hunter's is to realise their dream of building their own home and give their young family a space to create precious memories together.

"All we can do is take it day by day and focus on our mission to get Isla into her very own family home, make her life beautiful and make memories together," Nikita said.

"You think you have time for these things, but in an instant that time was taken away from us."

But Nikita admits it isn't easy and knows her family faces tough times ahead.

"I have extremely dark days where I can't escape my own mind, but when I look at what I have, this amazing little girl, I remember my duty as a mother which is to tell her story, one she can't tell herself," she said.

"We will never stop fighting for her or with her. We will fight back at Batten and not let it define her."