To students researching this subject for a school project:

XP is categorized in at least eight complementation groups according to the capacity of the body to repair DNA. These groups (i.e., genetic subtypes) are labeled A through G, plus the XP variant: XPV. Groups A, C, D, and Variant make up over 90% of XP cases. Group A, for example, has the lowest level of DNA repair and the most neurological manifestations.


  • Wide range of symptoms
    • blistering or freckling on minimum sun exposure
    • premature aging of skin, lips, eyes, mouth and tongue; with significant increased incidence of cancer in these same areas
    • blindness resulting from eye lesions or surgery for skin cancer close to the eyes
    • progressive neurological complications including:
      • developmental disabilities
      • mental retardation
      • high frequency hearing loss, progressing to deafness
      • de Sanctis-Cacchione syndrome (rare)
  • Very rare
    • Prevalence is estimated at 1:1,000,000 in the United States. Certain populations have a higher prevalence. For example, in Japan, the prevalence is estimated as 1:40,000. Prevalence is increased in communities in which consanguinity is common. (reference)
  • Clinical diagnosis possible
  • Life threatening
    • The DNA damage is cumulative and irreversible
    • Greater than 1000-fold increased risk of skin cancer, or pre-cancerous tumors and mouth and eye tumors
  • Other disorders associated with defective DNA repair
    • Ataxia-Telangiectasia
    • Bloom Syndrome
    • Cockayne Syndrome
    • Fanconi Anemia
    • Trichothiodystrophy (TTD)
  • Other disorders characterized by light sensitivity
    • Drug-induced photosensitivity
    • Erythropoietic Protoporphyria (EPP)
    • Lupus (30% of cases)
    • Polymorphous Light Eruption (PLE)
    • Porphyria (general)

There is no cure for XP. The DNA damage is cumulative and irreversible. Management is limited to avoidance of exposure to damaging UV radiation by staying indoors with sunlight blocked out, and use of protective clothing, sunscreens and sunglasses. Also, avoid other known carcinogens.

Regular surveillance for and treatment of all neoplasms is very important.

For the most complete and up-to-date coverage of this disease, please refer to this GeneReviews article:
Xeroderma Pigmentosum
[XP Includes: DeSanctis-Cacchione Syndrome]
by Daniel J. Wattendorf, MD and Kenneth H. Kraemer, MD.

Physicians seeking information about xeroderma pigmentosum will find a chapter on the subject written by W Clark Lambert, Claude E Gagna, Santiago A Centurion, Hon Li in the MOSBY book: Treatment of Skin Disease, edited by Mark Lebwohl, Warren Heymann, John Berth-Jones and Ian Coulson. Copywrite 2002.

XP defined on other Websites (Please use BACK function to return to this site):

Also, on this site, see:

Understanding Ultraviolet (UV) radiation, its effects upon the XP patient, its measurement, and protection from UV are all extremely important. Please review these resources:

[To pronounce xeroderma, see this page.]

Not sure of diagnosis?

Parents of children who seem to have some kind of light or sun sensitivity may want to consult a dermatologist and discuss the following with their physicians:
Photosensitivity in children:
An approach to diagnosis and management

The XP Society is the international authority for XP (xeroderma Pigmentosum) family support and information to assist in making intelligent decisions in the caregiving of XP family members.

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