The baffling case of Brooke Greenberg, a 20-year-old who never developed beyond the age of a toddler, may provide clues that will help scientists unlock the secrets of longevity and help fight age-related disorders, such as Alzheimer's, Parkinson's, and heart disease. Brooke, who passed away on Thursday, had the body and cognitive function of a one-year-old. She never grew at all after the age of five-basically, she stopped aging entirely. She may have been the only person in the world suffering from a mysterious genetic disease that her doctors called Syndrome X. "Finding out that her DNA makeup is completely different than anyone else's brought to our attention that we could help," Her father, Howard Greenberg, told Yahoo Shine in January. "So eventually, at the end of the rainbow, there will be something that comes out of all this. I believe everyone is here for a reason."

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Brooke's growth was erratic in the womb. "One month she would be fine, one month she would just stop and play catch up," Melanie told NBC Dateline. She was born a month prematurely and weighed only four pounds. She also had a rare form of hip dislocation, which required surgery. However, during her first year, her parents thought she would grow up and have a normal life. Between one and six, Brooke suffered a number of medical emergencies including perforated stomach ulcers, a seizure, and a stroke, and also stopped growing. Her parents consulted many specialists but none could diagnose a known endocrine or chromosomal abnormality. Doctors prescribed human growth hormone, which failed.

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Brooke's case was brought the attention of Dr. Eric Schadt, director of the Icahn Institute for Genomics and Multi-Scale Biology at Mount Sinai Medical Center in New York. His team began sequencing her DNA, looking for specific mutations related to her condition. "By creating stem cells from Brooke's skin," Schadt explained in an article he wrote for katiecouric.com after appearing on the program with the Greenberg family, "we have been able to make neurons, liver cells, fat cells, and other cell types from Brooke so that we can study the function of the 'special' genes we identified in Brooke and how they affect normal biological processes, processes associated with aging, and processes associated with disease." He added that this could lead to breakthroughs in how manipulating these genes might increase longevity across human populations. Her case could ""blow a whole field of science wide open," he said.

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While Brooke's mysterious condition may lead to amazing scientific discoveries, on a quieter and more intimate level, she also leaves behind an inspiring legacy of unconditional love. "While the outside world may have noticed Brooke's physical stature and been puzzled by her unique development state, she brought joy and love to her family," Rabi Andrew Busch, who spoke at her funeral on Sunday, told the Daily News. Throughout her life, her parents and three sisters cherished her and showered her with affection. She loved to be cuddled and tickled and her parents said she develped a strong identity and a rebellious streak. When her younger sister, Carly, was born, her parents described Brooke as jealous like any other child would be. And, despite the challenges the family faced over the years, their devotion never waivered. "The older she gets it's unbelievable…everybody just wants to hold her," mother Melanie Greenberg told WBAL. Her dad called her "his angel."

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