Story highlights Peggy Ickenroth photographed Suzanne, a 12-year-old with Prader-Willi syndrome

The genetic disorder's symptoms include an insatiable appetite

(CNN) Every morning, Rick Heijnen prepares his daughter the same breakfast at the same time with the same ingredients: crackers and biscuits, cheese and applesauce, peanut butter, gingerbread, orange juice, buttermilk, water.

To change her routine could mean a major meltdown. To change her diet could be catastrophic.

Suzanne Heijnen has Prader-Willi syndrome, a genetic condition that is estimated to affect one out of 10,000 to 30,000 people. Peggy Ickenroth met Suzanne a few years ago, when she was 12, and photographed her family over a two-week period, hoping to learn more about the disease and how it affects people.

Prader-Willi symptoms can include low muscle tone, developmental delays and difficulty controlling emotions. Indeed, Suzanne has problems with her spine, tires easily and is prone to furious outbursts over minor slights.

But the most prominent symptom of Prader-Willi is an insatiable appetite, which can lead to dangerous levels of obesity and myriad other health problems. She has been on a limited diet since age 2 and knew there were strict rules about what she could and could not eat.

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