In her heart, Lisa Davis knew something was wrong with her child.
A mother of four, she was no stranger to the challenges of childcare. But when her daughter Haley was 18 months old, she says, her behavior stood out as strange. And it seemed to revolve around an obsession with food.
"She was digging through the trash and eating everything, even raw meat," Davis recalls. "If we had had yogurt that day, she would lick the empty cup. She was eating butter. Anything she could find."
For more than three years, Davis searched for a medical explanation.
"The doctors kept telling me that she would outgrow it," she says. "But I knew in my heart that it was something more."
Last October, Davis's intuition turned out to be correct. A genetic test revealed that Haley, now 5, possesses a rare condition known as Prader-Willi syndrome. Among the hallmarks of the gene-linked disorder are small stature, behavioral and learning disabilities, and a ravenous appetite that can never be sated.
The Davis kitchen is now in a state of permanent lockdown. Every space in which food is stored, from the fridge to the kitchen cabinets, is under lock and key.
Still, Haley has occasionally found the keys.
"Every age is different as far as what you go through," Davis says. "As she got older, it became more of a manipulative thing. If she asked for food and I told her no, she would ask my husband; she would go to him and tell him that I told her yes."
+ "Everything around food is a big deal," she adds. "You need it to survive. But to have it be something that could kill your child...."
In the world of genetic disorders, Prader-Willi is a relative newcomer. The syndrome was first identified in 1956, though doctors at the time had little clue as to how it arose.
Decades later, in 1981, Dr. David Ledbetter, then a grad student at the University of Texas at Austin and now the director of the Division of Medical Genetics at Emory University's School of Medicine, was working with colleagues from Massachusetts General Hospital and Harvard. They discovered that many people with the syndrome were missing the same small stretch of genes on chromosome 15.
Dr. Merlin Butler, chief of medical genetics and molecular medicine at Children's Mercy Hospitals and a professor of pediatrics at the University of Missouri-Kansas City School of Medicine, says one theory behind the insatiable hunger may represent an adaptive measure gone haywire.
"From the clinical side, we know we all carry genes — the so-called thrift genes — which are there to help us try to store energy when availability becomes scarce," Butler explains, adding that these genes could be a throwback to a time when humans would have to be able to store and conserve energy in order to survive trying times.
"Now, during a time of excess, these genes are still doing their thing and making us obese," he says.
The condition is quite rare, Butler notes, as it affects only about one out of every 15,000 or 20,000 children. But this relative rarity may be the reason why so many children like Haley are only identified as having Prader-Willi years after signs of the condition emerge.