Children with a muscle-wasting condition called spinal muscular atrophy (SMA) will get a new breakthrough drug for just $40, instead of hundreds of thousands of dollars.

Key points: Access for life saving drug for genetic condition

Access for life saving drug for genetic condition The drug Spinraza helps patients with spinal muscular atrophy

The drug Spinraza helps patients with spinal muscular atrophy More than $240 million to be allocated to fund the drug

Health Minister Greg Hunt told the ABC from June 2018, Spinraza will be available on the Pharmaceutical Benefits Scheme (PBS) for the treatment of Type 1, Type 2 and Type 3a SMA for all patients under the age of 18.

"This will be both life-saving and life-changing for hundreds of young patients and their families," he said.

SMA is a rare, muscle-wasting genetic disorder that affects the motor neurons that control movement.

The most severe form, Type 1, can cause respiratory problems, extreme weakness and early death.

The disorder is the number one genetic killer in babies.

'Mackenzie's mission' to improve screening and treatment

In January 2018, Mr Hunt revealed his plan to the ABC to boost education, screening and treatment for genetic conditions.

He called it "Mackenzie's mission" after baby Mackenzie Casella, who died from SMA.

Mackenzie Casella was just seven months old when she died. ( Supplied: Rachael Casella )

Many families of children with SMA have been lobbying for the drug Spinraza to be put on the PBS.

In 2017, baby Aviana Mcelwee from Darwin was the first Australian child to trial the medication.

Over the course of treatment, now injected into Aviana's spine every four months, a baby who could previously only move her fingers and eyes began to hold up her head and peer around autonomously.

"She still can't crawl or walk but now she can sit, which a Type 1 isn't supposed to do independently," her mother Bethan McElwee said.

Do you know more? Contact specialist.team@abc.net.au.

The drug was approved by the Pharmaceutical Benefits Advisory Committee in April 2018, after being rejected in 2017.

"I have spoken to countless families about the need for this vital medicine and I know what a positive difference it will make," Mr Hunt said.

Clinical trials showed the drug could improve motor function and survival.

More than $240 million will be allocated in the federal budget to list the drug on the PBS.