When Brooke Greenberg was alive, no one could have guessed her age. But it wasn't one of those cases where an individual adopts a healthy lifestyle and thus looks much younger than they actually are. In Brooke's unfortunate case, it was a rare physical disorder that kept the 20-year-old's body similar to a toddler's.

Source: JaxObserver

 Yes, that is the picture of a 20-year-old Brooke Greenberg.

Brooke Greenberg was born with a condition so rare that it doesn't even have a name. Syndrome X, as the doctors call it, has apparently affected just 6 people in the world. When she died at the age of 20, Brooke was roughly the size of a 6-month-old toddler.

Source: FindAGrave

On January 8, 1993, Brooke was born to Howard and Melanie Greenberg. She was delivered a month before her due date and weighed just 4 pounds at birth. At the time of birth, she had her legs swivelled towards her shoulders, a condition that was surgically corrected. All through her childhood, she went through many medical emergencies. 

Once when she was four, she fell into lethargy and slept for 14 straight days. 

"We were preparing for our child to die," Howard Greenberg had told ABC in 2009. "We were saying goodbye. And, then, we got a call that there was some change, that Brooke had opened her eyes and she was fine. There was no tumour. She overcomes every obstacle that is thrown her way."

Source: HLNTV

But a little later, between the ages of four and five, her body stopped growing.

The Greenbergs took her to many specialists, but unfortunately, no doctor could pinpoint what was wrong with her.

A medical researcher from the University of Florida Medical School, Richard F. Walker, had followed the peculiar case of Brooke Greenberg since she was 2. According to Walker, Brooke's body could not develop as a coordinated unit, but as independent parts growing out of sync.

At the age of 16, she still had the teeth of a baby and the bones of a 10-year-old. Same with her brain, various parts grew at different rates, rather than developing together, a condition no doctor could explain. 

Source: ABC

Despite these challenges, Brooke's mannerisms changed as she grew. Her sisters fondly remember how she even used to rebel like a typical teenager sometimes. She couldn't speak but used sounds to express what she was feeling. She made it known what she liked and what she didn't.

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Brooke Greenberg's biological situation still remains a mystery, but researchers believe her genome could reveal secrets to longevity. 

Source: ABC

She may have passed away but her DNA could have answers to the secret, that is ageing.