Xeroderma pigmentosum is caused by mutations in genes that interfere with DNA repair after damage caused by ultraviolet (UV) radiation. (Image credit: Anadolu via Getty Images)
Disease name: Xeroderma pigmentosum (XP)
Affected populations: Xeroderma pigmentosum is a rare genetic disorder in which people's skin becomes overly sensitive to the damaging effects of ultraviolet (UV) light. XP can develop in both men and women and can affect people of various ethnic backgrounds.
XP is estimated to affect about 1 in a million people in the United States, but the disease is more common in other parts of the world, including Japan, North Africa, and the Middle East. For example, in Japan, XP is estimated to affect about 45 people per million.
Causes: XP is caused by mutations in genes that prevent DNA from repairing damage caused by ultraviolet radiation found in sunlight and some artificial light sources, including tanning beds. Unrepaired DNA builds up inside cells and causes a variety of symptoms.
Scientists have found eight different gene mutations linked to XP; the most common, at least in the U.S., is a mutation in a gene called XPC. The gene codes for an enzyme that plays a key role in detecting DNA damage, and the mutation renders the protein unable to do its job.
XP is an autosomal recessive disorder, meaning that for it to occur, a person must inherit two copies of the defective gene—one from each parent.
Symptoms: Symptoms of XP usually appear in infancy or early childhood. People with the condition often burn very easily in the sun—about half of children with XP will develop severe sunburn after just a few minutes of sun exposure.
XP patients may also develop freckles before age 2 on areas of the body that are typically exposed to sunlight, such as the face, hands, and lips. In addition, their eyes are often very sensitive to DNA damage caused by bright light. Repeated exposure to sunlight can also cause the skin to become dry, thin, and have a mixture of darker and lighter areas.
XP patients are strongly advised to avoid sunlight and wear protective clothing as a precaution.
People with XP are up to 2,000 times more likely to develop melanoma, a type of skin cancer for which ultraviolet radiation is a major risk factor. Without protection from ultraviolet radiation, people with XP are likely to develop skin cancer many times during their lifetime, most often for the first time at age
Sourse: www.livescience.com
