Noah Abraham Belton, who lived 17 years with a rare degenerative neurological disorder and whose courage inspired others and helped change public policy, died Aug. 26 at home in McLean. He was 20.

Mr. Belton, who was born in Washington and grew up in McLean, began showing signs of diminishing health at 41/2 and was diagnosed with Alexander disease at 10. Despite his illness, he continued his schooling, last attending Falls Church High School.

Though his physical abilities decreased sharply, Mr. Belton "had a liveliness about him that he seemed to express through his eyes and a smile," said Phillip Pearl, a pediatric neurologist who first encountered Mr. Belton when the youth was rushed to Inova Fairfax Hospital's emergency room in 1990.

It was later determined that the seizures Mr. Belton was experiencing were related to Alexander disease, which affects the white matter of the brain. A progressive genetic disorder, the disease occurs mostly in males and hinders their mental, physical and behavioral skills. It strikes one in a million people, limiting the average life expectancy to 10 years.

Mr. Belton "turned out to be a survivor in the end," Pearl said. "He taught us something about the wide spectrum and variability of the disease."

"Noah was an inspiration," he continued. "He had a sense of humor and warmth that permeated his personality and outlasted any neurological difficulties."

Mr. Belton also had an impact on those who could affect government policies, including Chuck Ludlam, then principal lobbyist for the Biotechnology Industry Organization. In 1997, Ludlam helped make permanent the Orphan Drug Tax Credit that funds research for rare diseases. Over the years, the tax credit had constantly been in jeopardy, and companies had little incentive to craft products for the small number of people with Alexander disease.

"The reason I took this on was Noah," said Ludlam, who had known Mr. Belton since he was born. "He influenced public policy. . . . It's fair to say that Noah, in this way, had helped to find therapies and cures for many others."

With the support of his family, Mr. Belton was an active member of the Langley Hills Friends Meeting in McLean.

He received the Principal's Award from Spring Hill Elementary School in McLean in 1994 in recognition of his "gift of friendship." In 1997, he was the first recipient of the Patti Hess Humanitarian Award from Buzz Aldrin Elementary School in Reston. The award honored him as "an individual who by deed, action or behavior is a role model for all of us."

Mr. Belton enjoyed his father's animated readings of P.G. Wodehouse and watching movies -- and sometimes cooking -- with his mother.

Survivors include his parents, Hugh and Jennifer Belton of McLean; two sisters, Sarah Belton and Julia Belton, also of McLean; and his grandfathers, William Belton of Great Cacapon, W.Va., and Frank DeToro of Reston.

In 2001, Mr. Belton was named an honorary firefighter at Fire Station 1 in McLean and was presented with a firefighter's helmet and badge. "Courage isn't just a uniform that firefighters put on," Lt. Tony C. Kostecka said at the time. "It's something that we carry around in our hearts. Noah has more courage than any of us will ever know."

Noah Belton suffered from a rare disorder.