Doctors Baffled, Intrigued by Girl Who Doesn't Age

ABC News- Brooke Greenberg is the size of an infant, with the mental capacity of a toddler.
She turned 16 in January.

"Why doesn't she age?" Howard Greenberg, 52, asked of his daughter. "Is she the fountain of youth?"

Such questions are why scientists are fascinated by Brooke. Among the many documented instances of children who fail to grow or develop in some way, Brooke's case may be unique, according to her doctor, Johns Hopkins School of Medicine pediatrician Lawrence Pakula, in Baltimore.

"Many of the best-known names in medicine, in their experience ... had not seen anyone who matched up to Brooke," Pakula said. "She is always a surprise."

Brooke hasn't aged in the conventional sense. 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 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, who include Pakula and All Children's Hospital (St. Petersburg, Fla.) geneticist Maxine Sutcliffe chronicled a baffling range of inconsistencies in Brooke's aging process. She still has baby teeth at 16, for instance. And her bone age is estimated to be more like 10 years old.

"There've been very minimal changes in Brooke's brain," Walker said. "Various parts of her body, rather than all being at the same stage, seem to be disconnected."

Brooke's mother, Melanie Greenberg, 48, sees a different picture. "She loves to shop," Greenberg said. "Just like a woman."

Brooke rides in a stroller while her mom shops for clothes in the infant sections of department stores near their home in a Baltimore suburb. That Brooke is in her mid-teens is so mind-boggling that if another mother with a toddler asks Greenberg how old Brooke is, she usually doesn't try to explain.

"My system always has been to turn years into months," Greenberg said. "So, if someone asked today, I might say, she's 16 months old."

CLICK HERE to see photos of Brooke through the years.

Watch "20/20" FRIDAY at 10 p.m. ET for Brooke's story.