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...

While high school kids have a reputation for being mean, everyone at Dana Hills High has welcomed McCoy with open arms.

Her classmates have taken her to Disneyland (once the sun sets, of course) and even organized a series of "Walk by the Light of the Moon" events, which raised over $300,000 for XP research. Sadly, this money won't be much help to McCoy or the other 100 people in America living with XPD.

Most people with this strain of the condition don't live past their 20s, and McCoy has already asked for her Make-a-Wish - a trip to Italy with her family. But at the start of her final school year, McCoy's friends left her with a touching way to remember them.

At the school's recent homecoming event, McCoy beat 6 other girls in a vote to win the coveted title of Homecoming Queen, and one of McCoy's friends flew in from his college in Nashville to crown her. McCoy said the moment was a "dream come true" for her, and we can't imagine a more perfect way to start the school year.

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[H/T: Mercury News]