Definition

A rare inherited disorder marked by an extreme sensitivity to ultraviolet light, such as from the sun, and a high risk of developing cancer. The signs and symptoms of XP are usually seen in children by age 2 years. Affected children may develop a severe blistering sunburn after a short time in the sun, freckling of the skin, dry skin, and changes in skin color in sun-exposed areas. They may also develop eye problems and problems with the nervous system. People with XP have a very high risk of developing skin cancer, usually by age 10 years, and other types of cancer, including cancers of the eyes, brain, and, in smokers, the lungs. XP is caused by mutations (changes) in certain genes involved in repairing damaged DNA. Also called xeroderma pigmentosum.