The six-year-old schoolgirl was born with a rare type of childhood interstitial lung disease (chILD) that prevents her from taking enough oxygen into her lungs and from clearing carbon dioxide from her body.

Sarah's been hospitalised more than 30 times and it's only this year that she's improved enough to allow her some freedom from the oxygen tanks that she has had to drag around to help her breathe.

"The first three years of her life were heart-rendingly horrific, but she's slowly improved to the point where we are now trialling keeping her off oxygen during the day.

"She still has high needs - she struggles with stamina and tires very easily, is fed through a gastrostomy tube in her stomach and sleeps with a ventilation mask to give her lungs a rest at night.

"But we have received so much support from charities such as the Steve Waugh Foundation, and Lindsay Park Public School has been able to provide her with a full-time teacher's aide to help with her feeding, mobility and personal care, so we are very lucky," Mrs Walker said.

Mrs Walker supports a push by Sarah's respiratory physician Professor Adam Jaffe and other experts for a national plan for rare diseases to ensure families can access help they need.

"It's very easy for families with children with rare diseases to slip through the cracks," she said. "These diseases are rare individually, but as a group they are common.

"So it's important that a national plan for rare diseases is created to make it easier for families to get information and support, and for research funding to become available."

Prof Jaffe, professor of paediatrics at Sydney Children's Hospital and UNSW, is using new research to lobby Australia's federal, state and territory governments to set up such a plan.

He will present the study, which will reveal for the first time the extent of rare diseases in Australia, at a scientific conference in Adelaide this week.

"Rare diseases, including rare lung diseases, are estimated to affect 6 to 10 per cent of the population, or 1.2 million Australians," he said.

"That equates to the number of people with diabetes. However because these diseases are so rare, patients don't get the same access to diagnosis and treatment as someone with a common disease.

"So we are calling for Australia to develop a national plan for rare diseases that will provide a framework around which we can make sure patients in this country with rare diseases get the appropriate and best care available," he said.