It was the 13th Great Illawarra Walk, and since 2018 all proceeds from the event have gone towards local research into Vanishing White Matter Disease.

Eleven-year-old Woonona girl Chloe Saxby and eight-year-old Holly Burns, from Mollymook, are among seven known cases of the degenerative brain disease in Australia.

There's no cure or treatment available, yet there is hope with the research team at the Illawarra Health and Medical Research Institute starting to see promising results.

Read more: Hope for families after breakthrough into Vanishing White Matter disease

Walk founder Chris Lovatt said the 2020 event had already raised more than $115,000 for the vital research.

"Our goal is $150,000, and with online donations until the end of the month, we're still confident of getting there," he said.

"Already the researchers have identified drugs that have a protective effect on VWMD cells, which can stop the deterioration of the disease hopefully until a cure can be found.

"This research in turn may have ramifications for other rare diseases."

One of the 736 walkers decked out in rainbow tutus and joggers on the day was Scott Muttdon, of BaiMed Physiotherapy, Woonona.

The cause is close to his heart, as he's been working with Chloe since she was a toddler.

"Chloe is great - she's cheeky and has a great sense of humour despite the challenges she faces," he said.

"So it's great to see the support for the cause from the community for this event - and the mood on the day is just incredible."

Mr Muttdon said he'd witnessed firsthand the effects of the disease - which will over time leave sufferers unable to walk, talk and eat.

A small bump to the head, a temperature, a cold or even a fright could be fatal - and most of those with the condition die before they reach their teenage years.

"When I started working with Chloe as a toddler, she could walk short distances by herself or with the help of a walking frame," he said.

"Now, due to her deterioration, physio is aimed at trying to allow her to maintain as much independence as possible - so she can sit upright to eat, so she can help mum and dad transfer her from her bed to her wheelchair or to the shower.

"She suffers a lot of muscle aches and pains and there are nights when she barely sleeps, so physio can be tough for her, but we keep it play-based and keep an eye on her goals."

Mr Muttdon said Chloe's parents Nyree and Grant did an amazing job supporting their little girl, while painstakingly working to raise awareness and funds for VWMD to help all sufferers.

Since its inception in 2008 the Great Illawarra Walk has raised more than $830,000 for children in need throughout the Illawarra, including Camp Quality and Wollongong Hospital's Neonatal Unit.