The most critical management goal for XP is UV protection. While XP patients do not repair damage from UV in exposed tissues, they react normally to visible light. Eradicating all exposure to UV radiation may not be attainable; efforts should be directed towards providing a safer environment. Environments with high UV levels, such as outdoors during daylight hours, require the most rigorous protection and avoidance. However, long periods of lower levels of exposure also cause the accumulation of UV damage. Patients and their families can be taught to recognize and avoid UV sources and to institute protective measures in their home, school and other areas where the patient will spend long periods of time.
Protective measures should be a daily routine for XP patients. These include topically applied, broad spectrum, sun preparations with an SPF (sun protection factor) of at least 30 or higher, that protect against both UVB (short wavelength UV 290–320 nm) and UVA (long wavelength UV 320–400 nm), sun protective lip balms and make-up. The first application of the day should cover all exposed skin surface areas and applications should be reapplied to uncovered skin (usually face, ears, neck and hands) several times during the day. Finding the most acceptable sun block may take trial and error.
Clothing should cover as much skin surface as possible and should include long pants, long sleeved shirts, socks and closed toe shoes, hats which cover the ears or UV blocking face shields and hoods, and UV blocking sunglasses with side shields. For daytime outdoor exposure gloves or mittens can be worn to protect hands. Clothing material should be tightly woven (e.g., denim) or double layered. A simple test of effective UV protection by clothing is to hold the material up to a bright light. Material that permits visible light to pass will not block UV. Commercially available clothing made from sun blocking material is available but may be expensive. One alternative is a laundry additive called SunGuard (https://sunguardsunprotection.com/index.php), which is advertised to increase the ability of clothing to block UV. They recommend regular washing of outer clothing (pants, shirts, jackets, socks, gloves, and hats) to increase UV protection. The cornea and sclera are also at risk, and XP patients should wear UV blocking sunglasses in areas of potential exposure. The glasses should ‘wrap around’ the eyes to protect the sides of the eyes and large enough to fully protect both lids. Rigorous use of these measures should be initiated as soon as the diagnosis of XP is suspected, and need to be the mainstay of lifelong protection.
The major source of UV is the sun. Although window glass blocks most UVB wavelengths, UVA can pass through glass (along with visible light). Extremely sensitive XP patients have burned through window glass. The Americans with Disability Act and other laws and regulations mandate that children with XP be provided with a safe educational environment. Windows in rooms where XP patients will be spending substantial amounts of time, such as at home, in a car, in day care or school, should be shielded from UV radiation. This can be done with clear UV protective film, or, in some cases, by creating a consistently safe distance from windows. Schools should make accommodations during fire drills and physical education activities, since leaving the building during these activities is not safe for children with XP. An Individualized Educational Plan should be developed to keep them protected from UV sources but involved in these activities.
Medical alert bracelets (http://www.medicalert.org/home/Homegradient.aspx) and carrying an information card about the condition in a purse or wallet can be helpful in emergencies when affected individuals may not be able to communicate their UV sensitivity.
Unshielded fluorescent lighting and bare halogen bulbs are potential UV hazards. Replacing unshielded fluorescent bulbs with incandescent lights or placing plastic shielding over fluorescent bulbs can substantially reduce the ambient levels of UV. Halogen lights emit substantial levels of UVB and should be avoided.
Relatively inexpensive hand-held UV meters can measure UVB and UVA. While the UVB radiation is more damaging, UVA radiation can also produce DNA damage, so protection from all wavelengths of UV is desirable. Meters can be effective learning tools; since the level of UV cannot be easily estimated, directly measuring UV in the environment provides patients and families greater ability to assess the safety of surroundings.
Vitamin D is produced in the skin by UV exposure. Rigorous sun protection may lead to low levels of vitamin D in the blood and can eventually lead to increased risk of bone fracture. Vitamin D rich foods such as ‘fatty’ fish and vitamin D supplemented milk can help maintain normal vitamin D levels; however, patients should have periodic monitoring of vitamin D levels and oral supplementation if the serum levels of 25-OH vitamin D are low.
XP patients should not use any type of tobacco products and should be protected from second-hand smoke. The benzo[a]pyrene derivatives and other carcinogens found in tobacco products and smoke induce DNA damage repaired by the NER pathway, putting the XP patient at high risk for oral and respiratory tract cancers.
The substantial lifestyle adjustment necessary to provide a safer UV environment can be a challenge for the family. Outdoor activities should be avoided during daylight hours particularly between 10 am and 2 pm. Identifying appropriate indoor play and sports activities for the affected XP child, while continuing to meet the needs of the unaffected family members, can be difficult.
