SAN DIEGO -- A North County family is uniting to find a cure for a rare, crippling autoimmune disease called juvenile dermatomyositis.

Four years ago, Parker Hume was a typical 4-year-old.

But gradually, normal movements for Parker became impossible.

Shari Hume, Parker’s mother, said, “He couldn’t take a step without falling.”

Parker’s small and once-healthy body was waging war against a rare autoimmune disease called juvenile dermatomyositis, also known as JM. About 3 children out of one million have JM.

"Your immune system goes haywire, you get inflammation in the muscles and it's creating damage in the muscles over time,” said Parker’s father Tom Hume.

Rady Children’s Hospital rheumatologist Dr. Robert Sheets said, “It was this pattern of weakness that was the tip-off for the diagnosis."

It would take about six months and dozens of tests before Parker’s parents knew what they were up against.

"With this disease, everything is out of control and it’s like this dark cloud looming over you. You don't know when it's going to come back," said Tom Hume.

Some children with JM will go into remission, others battle the disease on and off their entire lives and some will suffer from crippling side effects, or even death.

Every few weeks, Parker comes to Children’s Hospital to receive intravenous medications that will strengthen his bones and help reduce inflammation in his muscles.

The drugs have given Parker the ability to walk again, but over time, the potent steroids could take a tremendous toll on his body, leading to osteoporosis and other serious health problems.

In Parker’s case, the frequent infusions of medication are keeping his disease in check and allow him to realize his dream of playing baseball.

“I want to be a baseball player,” Parker told 10News.

Because of his disease, Parker only started playing baseball two years ago, but he’s already an accomplished player.

"I think his strength and resilience is humbling to us as parents and gives everyone strength in the family because we all pull together and become this really cohesive unit...We're in it together," said Shari Hume.

The Humes and a Vista woman whose grandson has JM have formed the Cure JM Foundation.

The foundation has already funded a significant amount of research and recently approved a $1 million grant to establish a program of excellence in JM research.

The foundation has also funded the first-ever book about JM written by leading specialists, a book dedicated to Parker.

For more information about Cure JM, visit the foundation’s Web site.