A 17-year-old with a rare genetic condition that causes premature aging passed away Thursday night.

Hayley Okines was told by doctors she would not live past the age of 13 because of a rare genetic disease called progeria, according to The Washington Post. The disease caused her body to age eight times faster than the average person.

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"My baby has gone somewhere better.  She took her last breath in my arms at 9:39pm," Hayley's mom, Kerry, wrote on Facebook Thursday night.  

Okines had been in the hospital being treated for pneumonia, according to the BBC.

Okines had released two books about her life, "Old Before My Time" and "Young at Heart," and had starred in several TV documentaries talking about living with progeria.  She also took part in an experimental drug treatment in the U.S., living four years beyond the average life expectancy of people with progeria.  

"The entire Progeria family mourns together with many as we say goodbye to Hayley Okines, our smart, beautiful and spirited English Rose," the Progeria Research Foundation wrote on Facebook. "We will miss you."