Xeroderma Pigmentosum (or XP) is a rare inherited disease affecting both males and females. It causes a person to be extremely sensitive to the damaging effects of ultraviolet radiation. Undiagnosed and untreated, XP can lead to the early onset of skin cancer and blindness. In addition, approximately 20% of the people with XP develop progressive neurological disease.XP is an autosomal recessive disease caused by mutations in genes that are critical for DNA repair. The body must repair DNA when it is damaged by harmful external agents such as ultraviolet radiation, X-rays and chemicals. There are at least eight genes that are critical for this DNA repair process. If a person is born with any of the eight genes not functioning correctly, he or she will develop the symptoms of XP. The genes for XP are: XP-A, XP-B, XP-C, XP-D, XP-E, XP-F, XP-G, and variant XP. Prior to the discovery of the XP genes themselves, the term “complementation groups” was used to describe the laboratory variations seen in the cells of XP patients. The cells were categorized according to the capacity of the cells to repair DNA after they had been damaged by ultraviolet radiation in the laboratory. Mutations in the A, C, D, and Variant genes make up over 90% of XP cases.
How is XP diagnosed?
Often the first people to suspect that, something is “wrong” are the parents. Many parents notice that in early infancy around 1-2 years of age their children will have unusually dark freckles (lentigos) or will have had severe sunburns after only being in the sun a few minutes. A thorough skin exam by a dermatologist, along with a small skin biopsy for laboratory testing, is the standard method for diagnosing XP. Xeroderma Pigmentosum can usually be conclusively diagnosed by measuring the DNA repair function from the skin cells obtained from the biopsy.
Early onset of freckling, (before age 2) especially in sun exposed areas of the skin, severe burns after only a short duration of sun exposure or exposure to ultraviolet lights. Some people with XP may develop burns even in shady areas.
- Blistering or freckling after minimal sun or ultraviolet exposure
- A dry, premature-aged appearance to the skin and lips
- Photosensitivity of the eyes (become red and sore when exposed to the sunlight)
- Early onset of skin cancer in any skin, including the tip of the tongue
Progressive Neurological Complications
- Developmental disabilities
- High frequency hearing loss, progressing to deafness
- Loss of previously attained abilities such as walking and talking
What is the treatment for XP?
The main goal of treatment is protection from UV exposure and thus prevention of the damaging effects it can have on the skin. There is currently no cure for XP. What is the prognosis? Many patients with xeroderma pigmentosum die at an early age from skin cancers. However, if a person is diagnosed early, does not have severe neurological symptoms or has a mild variant, and takes all the precautionary measures to avoid exposure to UV light, they may survive beyond middle age. Patients with xeroderma pigmentosum and their families will face many challenges in daily living. Constant educating and reminding of the need to protect oneself from sunlight is paramount to the management of xeroderma pigmentosum.