A child with XP wears a NASA designed UV-protective suit.

To the "Children of the Moon," nighttime at Camp Sundown is the time to go outside and enjoy nature. These children suffer from a rare disease that makes a suntan a potentially fatal experience; their skin is often damaged so that it resembles that of old people who have spent too many years in the Sun.

This life-threatening disease is called xeroderma pigmentosum, XP for short. XP is incurable and very rare; there are fewer than 1,000 XP patients worldwide. People with XP are extremely sensitive to ultraviolet light. What makes the disorder so serious is that any DNA damage from sunlight is irreversible and accumulates throughout the patient's lifetime.

For most of us, there are ways for the body to repair that damage. But XP patients are born with a rare genetic defect—their bodies are unable to repair damage to DNA from ultraviolet light. Children with XP are especially prone to skin and eye cancers. Because of this, they have to avoid known carcinogens that damage DNA. Regular visits to the doctor are a must, checking for cancers. Very often, an XP child's first skin cancer appears before the age of 12.

For an XP patient, just being outdoors can cause severe damage. In fact, XP sufferers have to take special precautions to block UV light from entering their homes; they can go out only at night. Indoors, their houses have to be modified to block sunlight—using curtains or special UV-absorbing window films. XP children have to wear protective clothing, sunscreens, and sunglasses.

Incandescent bulbs cause no harm to XP patients, but bare fluorescent bulbs may be a hazard. The manufacturer of NASA's space suits has been exploring the design of a cooled, UV-absorbing space suit for XP children to wear. The design would be similar to what the astronauts currently wear, since they are exposed to high levels of UV when working in space.

The lives of XP patients give us insight into what our world might be like if the ozone layer in the upper atmosphere were thinner or even nonexistent. Damage to our DNA would be much greater, and our repair mechanisms to "fix" DNA damaged by the Sun would be overwhelmed. We would develop skin cancers at a much faster rate, and our skin would age rapidly. Living on other planets that do not have an ozone layer would also be dangerous, given the ultraviolet light emitted from the Sun.

Image courtesy of the HED Foundation. ©2001 www.hedfoundation.org