Brooke Greenberg is 20 years old, but she looks much, much younger. In fact, despite her age, she closely resembles a toddler, both physically and mentally.

Brooke’s family appeared on Katie Couric’s television talk show “Katie” to discuss their daughter’s condition. And while Brooke clearly has a severe disorder that prevents her from aging past the level of a toddler, doctors have never been able to explain exactly why.

The Daily Mail recapped much of the family’s appearance on “Katie” and provided several pictures of Brooke, her sister, and other members of her family.

Brooke’s father, Howard Greenberg, said that, at first, there appeared to be nothing seriously wrong with his daughter. But, by age 5, she had stopped growing.

“From age one to four, Brooke changed. She got a little bit bigger. But age four, four to five, she stopped,” Greenberg explained on “Katie.”

Since then, her family has taken her to several top medical specialists in the U.S., but no doctor has been able to accurately diagnose Brooke’s illness. Instead, researchers have taken to calling her rare and peculiar list of symptoms “Syndrome X.”

On the “Katie” talk show, Dr. Eric Schadt, director of the Institute for Genomics and Multiscale Biology at the Mount Sinai Medical Center in New York, explained that, on the surface, there appears to be no specific cause blocking Brooke’s development.

“[Brooke has] no apparent abnormalities in her endocrine system, no gross chromosomal abnormalities, or any of the other disruptions known to occur in humans that can cause developmental issues,” Schadt told Couric.

And it isn’t just development that is a problem for Brooke and her family. Because of the intense complications of Brooke’s disease, and because she is still mentally at the level of a toddler, her parents are required to care for her 24 hours a day.

Brooke cannot even eat on her own and must be fed through a tube in her stomach because of complications with her esophagus, according to the Daily Mail. Brooke has also suffered several medical emergencies, including stomach ulcers, a brain seizure, and a two-week-long coma.

Despite all the hardships the Greenberg family has endured, Schadt said he is confident that with the right kind of research, scientists may be able to better understand Brooke’s condition and use that knowledge to fight aging. In fact, Schadt said he believes that we have a lot to learn based on Brooke’s unique genetic code.

“Manipulating these genes [that stunt Brooke’s development] could increase longevity and/or reduce aging-related disorders such as Alzheimer’s, heart disease, and many forms of cancer,” Schadt told Couric.