The amazing story in a nutshell: Brooke Greenberg, already 16 years old, still has the body of an infant; she stopped growing when she was two. Brooke's medical condition has left her with the mental and verbal capacity of a toddler. She's also had several bouts with tumors, cancers, and seizures, all from which she recovered quickly.
So far the only person known to have this condition, Brooke has baffled specialists. Brooke may hold the key to why and how humans develop and grow old. They're analyzing her DNA to determine specific mutations. However, she has not been diagnosed with any genetic syndrome or chromosomal abnormality.
The lead doctor involved in Brooke's case, Richard Walker, has a web site chronicling his findings. The original case study is available for download.