Brooke Greenberg may appear to be no older than 4 or 5, but the girl, who suffers from a mysterious medical disorder, is actually 20 years old. Her extremely rare condition, dubbed "Syndrome X," has puzzled medical professionals for years. Even some of the world's leading experts have been unable to find a medical precedent for her stunted development. However, one doctor believes that studying Brooke's biology could offer clues to other mysteries of the human body.