Xeroderma pigmentosum is a rare genetic disorder that affects the skin, the eyes, and sometimes the nervous system. It disrupts the body’s ability to repair damage from sunlight and other sources of UV light.
Approximately 1 in 1 million people in the United States have xeroderma pigmentosum (XP).
The symptoms of XP typically appear during infancy, and it is important to let a doctor know if there is sun damage, such as blistering, on an infant’s skin after minimal exposure to sunlight.
Below, learn what causes XP, how to manage it, and more.
XP is a rare genetic disorder that healthcare professionals characterize as extreme sensitivity to UV radiation. People with XP are especially susceptible to skin damage from the sun, including burns, blisters, and freckles.
The condition prevents the skin from repairing damage from UV light, and it can also cause neurological symptoms in some people.
The symptoms of XP can differ — some people may experience more symptoms than others, and the severity can range from mild to severe.
The symptoms typically affect the skin, the eyes, and sometimes the nervous system:
Effects on the skin
The National Organization for Rare Disorders (NORD) report that any area of skin that comes into contact with sunlight is susceptible to XP-related damage, including the tip of the tongue. The effects are typically more prominent on the eyelids and the surface of the eyes.
People with XP may also develop lentigines, or patchy freckling of the skin. This typically appears before the age of 2 years.
Other symptoms include:
- xerosis, or dry skin
- increased skin pigmentation
- skin atrophy, or thinning
- telangiectasia, the widening of small blood vessels resulting in thread-like patterns on the skin
Effects on the eyes
Symptoms that affect the eyes occur in approximately 80% of people with XP. A person may experience photophobia, or light sensitivity.
The eyes may become bloodshot and irritated, and the corneas, the clear protective outer layers of the eyes, can become cloudy.
A person may also develop dry eye, which can result from chronic inflammation of the cornea, or keratitis. In severe cases, keratitis can result in obscured vision and vision loss.
Repeated sun exposure may also affect the eyelids, causing them to thin and the eyelashes to fall out.
According to NORD, 25% of people with XP develop progressive neurological symptoms, which include:
- hearing loss
- limited coordination
- difficulty walking
- progressive cognitive impairment
- reduced muscle control
- difficulty talking and swallowing
People with XP also have an increased chance of developing of skin cancer.
The risk of developing nonmelanoma skin cancer, such as basal cell carcinoma or squamous cell carcinoma, is 1,000 times higher among people with XP, compared with the general population. Squamous cell carcinoma may form on the tip of the tongue, for example.
The risk of developing melanoma is 2,000 times greater. Among people with XP who develop melanoma, this typically happens at about the age of 22.
The National Institutes of Health (NIH) report that most people with XP develop some type of cancer by the time they reach early adulthood.
XP is an autosomal recessive genetic disorder. But what does this mean?
People inherit two copies of every gene, one from each parent. Genes are small parts of a chromosome.
“Recessive” means that both copies of the gene must have the characteristics of XP for the child to have the condition. “Autosomal” means that the affected gene is on a non-sex-determining chromosome.
XP can result from nine possible genes that are not working as they should. Many of these genes are important for repairing DNA damage.
Typically, skin cells repair this damage before it becomes a problem, but this process is disrupted in people with XP.
There is currently no cure for XP. Doctors and people with the condition typically focus on managing and preventing symptoms.
Specialists that may be involved in the care of someone with XP include:
- medical geneticists
Anyone with XP needs to visit a dermatologist every 6–12 months so that they can check for signs of cancer. A person also needs to have regular vision, hearing, and neurologic exams.
People with XP should reduce exposure to UV light as much as possible. A common source is sunlight, so it is crucial to wear the following while outdoors:
- protective clothing, including hoods, gloves, and UV light-blocking face shields
- protective sunglasses
A person can also use UV light-blocking film on their windows.
Other sources of UV light to avoid include:
- sun lamps
- tanning beds
- black light lamps
- xenon lights
- plasma flashlights
- welding arcs
As sunlight is a primary source of vitamin D, people with XP should take vitamin D supplements.
Cigarette smoke can also cause DNA damage, so people with XP should avoid smoking and secondhand smoke.
Doctors first assess the symptoms. They inspect areas of skin damage and ask about sun exposure habits and patterns.
If they suspect that XP is present, they may order a genetic test to confirm the diagnosis.
Many people with the condition have no family history of it.
People with XP have inherited the genetic characteristics from both parents. The chances of two parents with genes for XP having a child with the condition is 25%.
The condition can develop anywhere, but it appears to be more common in some countries. For example, in the U.S., XP affects 1 in 1 million people, but it affects 1 in 22,000 people in Japan.
There is no cure for XP. While many people with XP develop skin cancer at an early age, a person with the condition may live beyond middle age if they:
- receive the diagnosis and start taking precautions early
- experience no severe neurological symptoms
- have a mild variant of XP
- take every precaution to avoid UV light exposure
The symptoms of XP typically appear during infancy. Consult a doctor if there is sun damage on an infant’s skin after minimal exposure to sunlight.
An early diagnosis is important for managing the symptoms and improving the outlook. Let a doctor know about any persistent signs of the condition.
XP is a rare genetic disorder that causes sensitivity to UV light. It results from a genetic difference that limits the body’s ability to repair DNA damage.
Symptoms of XP can affect the skin, eyes, and nervous system. Some, such as cognitive impairment, worsen over time.
The best way to manage XP symptoms is to avoid sunlight and other sources of UV light. People with the condition have an increased risk of cancer and need to attend regular screenings.