Brooke Greenberg, Who Had Rare Genetic Disorder Labeled ‘Syndrome X,’ Dies At 20

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A young woman, who had a rare genetic disorder that puzzled doctors throughout her life, passed away at the age of 20.

Brooke Greenberg remained physically and cognitively similar to a toddler, with an estimated mental age of nine months to one year, according to She died last week and the cause of death remains unknown.

During an appearance on Katie Couric’s talk show earlier this year, the Greenberg family discussed how Brooke was unable to talk, still had her baby teeth and traveled in a stroller, like any infant. Doctors had never been able to explain the condition.

The New York Daily News reports that doctors eventually called Brooke’s extremely rare condition "Syndrome X."

In the womb, Brooke would not develop one month and play catch-up the next but that stopped around the age of 5 when all development stopped, her parents had told NBC News, according to The New York Daily News.

She was born one month early at just four pounds with a rare condition anterior hip dislocation. She needed surgery because her dislocated hips pushed forward and put her legs in an awkward position, a pediatrician explained.

The Greenberg family realized something was wrong as Brooke's younger sister aged past her, so they brought her to see many different specialists in search of answers. However, her condition was puzzling to all of them and scientists reportedly studied Brooke's DNA in hopes to learn more about human aging and extending youth.

Tests reportedly showed that Brooke may have suffered from a gene mutation that switched off her ability to mature.

Sources:, New York Daily News