Just 300 unlucky people in America have xeroderma pigmentosum, and Riley McCoy is one of them.
The 17-year-old high school student is a "moon child," who has to avoid direct sunlight at all costs. Even very brief exposure to the sun can cause blisters, skin cancer, or internal organ damage. Her body is simply missing the antibodies that protect the rest of us from the sun's rays.
To live a normal life from day to day, McCoy and her parents have made a lot of changes and sacrifices. Their home and car have tinted windows, and Riley wears gloves with a plastic UV-blocking hood from NASA to walk from the parking lot to school.
In fact, her parents chose McCoy's high school, Dana Hills High, specifically so Riley could walk between classes without passing under the sun. She can walk outside safely after the sun sets, but she still always checks the light's strength using a special tool before she steps outside.
Her condition has another dangerous side effect. McCoy has an especially rare strain of XP called XPD. It affects the antibodies that repair her brain as well as her skin. This is making her "age" before her time, and her parents guess that she has dropped 20 IQ points since starting high school.
That's a lot to deal with at a young age, which is why her friends organized a touching surprise for Riley at this year's homecoming...