XP is an extremely rare genetic skin condition for which there is no cure. It affects less than 100 people in the UK and is characterized by an extreme sensitivity to ultraviolet (UV) rays. UV is in sun light and a lot of artificial lighting. Unless patients with XP are protected from UV, their skin and eyes will become severely damaged which leads to cancer.
UV light damages the DNA in the skin and eyes of people with XP and they are unable to repair this damage. This damage presents itself as severe sunburn, abnormal freckles and sometimes eye problems. The damage to the DNA builds up and causes cancerous cell changes, meaning that people with XP are 1000 times more likely to develop skin cancer. In some people XP can also cause problems with the nerves or brain.
UV light is not just sunlight but daylight, so someone with XP would be at risk outside on cloudy wintery days as well sunny, summery days. The only ‘safe’ time to be outside is when it is dark. Even when indoors, people with XP can be harmed by daylight coming through windows and from the UV light that is emitted by many light bulbs.
Complete protection from UV light should prevent people with XP from developing skin cancer and with this careful protection, they can lead normal active lives.