She is the size of an infant, has all her baby teeth and exhibits the mental capacity of a toddler.
Trouble is, she's 16 years old.
Brooke Greenberg hasn't aged in the conventional sense. Her physician, Dr. Richard Walker of the University of South Florida College of Medicine, in Tampa, says Brooke's body is not developing as a coordinated unit, but instead as independent parts that are out of sync. She has never been diagnosed with any known genetic syndrome or chromosomal abnormality that would help explain why.
In a recent paper for the journal "Mechanisms of Ageing and Development," Walker and his co-authors chronicled a baffling range of inconsistencies in Brooke's aging process, including the observation that her bone age is like that of a 10 year old.
Walker and his team have studied samples of Brooke's cells and DNA to look for what they think may be an undiscovered genetic mutation that has affected the way she ages. He believes that if the gene can be isolated, it may provide clues to questions about why we age and die. If the gene -- or complex of genes -- is identified, he plans to test laboratory animals to determine whether the gene can be switched off and, if so, whether it will cause the animal's aging to slow.
"Without being sensational, I'd say this is an opportunity for us to answer the question, why we're mortal, or at least to test it," Walker said. "And if we're wrong, we can discard it. But if we're right, we've got the golden ring."