Teen Who Brought Hope to Those With 'Aging Disease' Dies From Rare Disorder

— -- A teen who brought awareness and hope to those suffering from a rare genetic disease that causes premature aging has died. She was 17.

Hayley Okines, of Bexhill, England, managed to survive four years longer than doctors predicted after she was diagnosed as an infant with the genetic disorder Hutchinson-Gilford syndrome, more commonly known as progeria.

She died after a brief battle of pneumonia, according to BBC News, and her death was confirmed by the Progeria Research Foundation.

Audrey Gordon, executive director for the Progeria Research Foundation, said Hayley had helped educate millions about the rare disease.

"She was a pioneer -- one of the first participants in the clinical drug trials and other research that initiated our progress toward treatments and cure -- and one of the reasons that we now have the first treatment for Progeria," said Gordon. "It took tremendous courage and determination by Hayley, her family and others like them to bring us to this point of progress, and we join her family and millions of people around the world in mourning her passing."

Hayley had helped raise awareness about her rare disease by posting about her progeria online and co-writing two books about growing up with the disorder, the first published when she was 13.

Progeria is an extremely rare genetic disorder and affects one out of every 4 million to 8 million births, and an estimated 250 children have the disease across the globe, according to the Progeria Research Foundation. The disorder causes children to age prematurely at a rate somewhere between eight and 10 times faster than normal children. Symptoms of the disorder include baldness, stunted growth and a loss of fat in their bodies.

Children with progeria report symptoms of aging at extremely young ages, including arthritis, osteoporosis and cardiovascular disease. Children often die due to cardio-related events around age 14, according to the Progeria Research Foundation.

In an interview with ABC News' "20/20" in 2011, Hayley's mother Kerry Okines said her daughter's health was "always" on her mind.

"The first thing I think about when I get up in the morning, 'Is today going to be the day that we lose her?'" Okines said in 2011.

Hayley was one of just a handful of children diagnosed in the United Kingdom. She was given treatment in a clinical trial in an effort to stall the deterioration by her premature aging.

"I feel like I have a future to plan," she told ABC News in a 2012 interview. "I think that maybe when I grow up, I will get married. Mum says it will have to be someone very special to see beyond my progeria."

Hayley said during that interview that she felt the treatment helped her become "stronger and taller."

ABC News' Jane E. Allen contributed to this report.