A story about a handful of girls who have “syndrome X,” a rare disease that keeps their bodies in what seems to be a permanent state of infancy:

Brooke was born a few weeks premature at just over 4 pounds. She had many birth defects, including moderate hearing loss, dislocated hips and dysmorphic facial features. Her brain had abnormally large chambers of fluid and lacked a corpus callosum, the bundle of nerve fibres that connects the right and left hemispheres. She had trouble swallowing, and by six months was eating through a feeding tube in her stomach. She always coughed and wheezed. Her paediatrician labelled her with “syndrome X”, not knowing what else to call it.

By age three, Brooke had reached 12 pounds, and she hovered around that weight until age 12, when she appeared on Dateline. After watching the show, Walker tracked down Howard Greenberg’s address and sent him a letter about his scientific background and his interest in Brooke’s case. Two weeks went by before Walker heard back, and after much discussion he was allowed to test Brooke. He was sent Brooke’s medical records as well as blood samples for genetic testing. In 2009, his team published a brief report describing her case.