According to Skin Cancer Foundation, xeroderma pigmentosum is a very rare genetic disease that causes high sensitivity to ultraviolet radiation, otherwise known as photosensitivity. The disease causes affected individuals to be extremely sensitive to sunlight. Prolonged exposure to the sun in these individuals can cause malignant tumors to develop much more frequently than the normal population. These tumors sometimes prove to be fatal.
The disease also causes the skin to age rapidly and become discolored, according to Skin Cancer Foundation. Damage done to a person's DNA by the sun's UV rays is a common occurrence, and in healthy individuals, the body is able to repair the damage before the DNA has a chance to replicate. In individuals with XP, their bodies do not repair this damage, and the damaged DNA replicates, which causes the abnormal skin growths that lead to tumors and skin cancer. XP is also characterized by poor eyesight, light sensitivity and conjunctivitis. As of 2014, there is no treatment for the disease. However, preventative measures can be taken to prevent the possibility of skin cancer, including avoiding as much sunlight as possible and covering exposed areas with a high SPF sunscreen if one must go out in the sun.