Xeroderma pigmentosum (XP) is a group of rare inherited skin disorders characterized by a heightened reaction to sunlight (photosensitivity) with skin blistering occurring after exposure to the sun. In some cases, pain and blistering may occur immediately after contact with sunlight. Acute sunburn and persistent redness or inflammation of the skin (erythema) are also early symptoms of XP. In most cases, these symptoms may be apparent immediately after birth or occur within the next three years. In other cases, symptoms may not develop until later in childhood or, more rarely, may not be recognized until adulthood. Other symptoms of XP may include discolorations, weakness and fragility, and/or scarring of the skin.

Xeroderma pigmentosum affects the eyes as well as the skin, has been associated with several forms of skin cancer, and, in some cases, may occur along with dwarfism, mental retardation, and/or delayed development.

Several subtypes of XP (i.e., XP complementation groups) have been identified, based upon different defects in the body's ability to repair DNA damaged by ultraviolet light (UV). According to the medical literature, the symptoms and findings associated with the classic form of xeroderma pigmentosum, known as XP, type A (XPA), may also occur in association with the other XP subtypes. These include: XP, type B (XPB); XP, type C (XPC), XP, type D (XPD); XP, type E (XPE); XP, type F (XPF); and XP, type G (XPG). These XP subtypes are transmitted as an autosomal recessive trait. In addition, another subtype of the disorder, known as XP, dominant type, has autosomal dominant inheritance.

In addition to the XP subtypes discussed above, researchers have identified another form of the disorder known as XP, variant type (XP-V). As with the other XP subtypes, symptoms and findings associated with the classic form of XP may also be seen in individuals with XP-V. XP-V cells have a normal or near normal ability to repair UV-induced DNA damage (nucleotide excisional repair), however, they are defective in replicating UV-damaged DNA during the division and reproduction of cells. Although the disorder's mode of inheritance is unknown, most researchers suspect that XP-V is transmitted as an autosomal recessive trait.

The signs of xeroderma pigmentosum usually appear in infancy or early childhood. Many affected children develop a severe sunburn after spending just a few minutes in the sun. The sunburn causes Redness and blistering that can last for weeks. Other affected children do not get sunburned with minimal sun exposure, but instead tan normally. By age 2, almost all children with xeroderma pigmentosum develop freckling of the skin in sun-exposed areas (such as the face, arms, and lips); this type of freckling rarely occurs in young children without the disorder. In affected individuals, exposure to sunlight often causes dry skin (xeroderma) and changes in skin coloring (pigmentation). This combination of features gives the condition its name, xeroderma pigmentosum.

Xeroderma pigmentosum is caused by mutations in genes that are involved in repairing damaged DNA. DNA can be damaged by UV rays from the sun and by toxic chemicals such as those found in cigarette smoke. Normal cells are usually able to fix DNA damage before it causes problems. However, in people with xeroderma pigmentosum, DNA damage is not repaired normally. As more abnormalities form in DNA, cells malfunction and eventually become cancerous or die.

Many of the genes related to xeroderma pigmentosum are part of a DNA-repair process known as nucleotide excision repair (NER). The proteins produced from these genes play a variety of roles in this process. They recognize DNA damage, unwind regions of DNA where the damage has occurred, snip out (excise) the abnormal sections, and replace the damaged areas with the correct DNA. Inherited abnormalities in the NER-related genes prevent cells from carrying out one or more of these steps. The POLH gene also plays a role in protecting cells from UV-induced DNA damage, although it is not involved in NER; mutations in this gene cause the variant type of xeroderma pigmentosum.

The major features of xeroderma pigmentosum result from a buildup of unrepaired DNA damage. When UV rays damage genes that control cell growth and division, cells can either die or grow too fast and in an uncontrolled way. Unregulated cell growth can lead to the development of cancerous tumors. Neurological abnormalities are also thought to result from an accumulation of DNA damage, although the brain is not exposed to UV rays. Researchers suspect that other factors damage DNA in nerve cells. It is unclear why some people with xeroderma pigmentosum develop neurological abnormalities and others do not.

Inherited mutations in at least eight genes have been found to cause xeroderma pigmentosum. More than half of all cases in the United States result from mutations in the XPC, ERCC2, or POLH genes. Mutations in the other genes generally account for a smaller percentage of cases.

Treatment for xeroderma pigmentosum, a variant type, can be challenging. The best thing you can do is to stay out of the sun as much as possible.

There is no cure for XPV, but there are treatments to help manage the condition.

The main treatments for XPV include:

• Avoidance of sun exposure and use of sunscreen
• Regular monitoring of the skin
• Excision of any cancerous lesions on the skin
• Sunscreen: Always use sunscreen when going outside.
• Avoiding air pollution: Air pollution can cause DNA damage and increase your risk of developing cancer.
• Diet: Eat a healthy diet that includes plenty of fruits and vegetables. This will help protect your skin from sun damage and other environmental effects.

People with xeroderma pigmentosum, variant type, have a reduced ability to repair UV-induced DNA damage. As a result, they are at risk for skin cancer and eye problems such as cataracts or blindness.

• They also have an increased risk of developing other cancers including leukemia, lymphoma and brain tumors.
• The risk factors for xeroderma pigmentosum, variant type are not fully understood.
• Researchers believe that the disorder is inherited as an autosomal recessive trait. This means that in order to develop the disease, you must inherit a single copy of the defective gene from each parent.
• Being fair-skinned and red-haired
• Living in a sunny area with high levels of ultraviolet radiation exposure (e.g., the tropics or southern regions of the United States)