Reposted from ABC News 7

WESTCHESTER COUNTY, New York (WABC) --

Among the more than 50,000 runners preparing to compete this Sunday is a teenager from Westchester County, who just a few years ago struggled to walk much less run.

Brian Lilly was diagnosed with rheumatoid arthritis at the age of 6.

"I was never really inclined to share with other kids that I had arthritis," Lilly said. "I tried to keep it a secret."

That secret became more difficult to keep as he grew older. Lilly was among roughly 300,000 children in the U.S. who suffer from the painful, joint-swelling disease, which is normally associated with older adults.

As a child, Lilly never imagined he would one day run in a marathon. But during his freshman year of high school, his symptoms began to decrease.

That's when Lilly began pushing himself to be more active and eat better. His hard work eventually began to pay off.

Now at the age of 18, he has undergone an amazing transformation and is even the captain of a rowing team.

"I've come a long way since the worst of my experiences with disease and through rowing, a lot of exercise, research and medication," he said. "I've overcome practically all of my symptoms of arthritis and I no long take medication."

Lilly is now planning to run his first marathon on behalf of the Arthritis Foundation. He wants to raise money and set an example for other kids who are struggling with health issues.

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