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Because Xeroderma Pigmentosa (XP) is a rare disease that causes extreme sun sensitivity and is usually diagnosed in childhood, it is a popular research subject for students.


The most important thing for students to understand is that people with XP are just like you. The biggest difference is that they can't go outside and play until dark. Even a small amount of sun exposure can have devastating affects. 

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, degenerative and irreversible

  • Greater than 2000-fold increased risk of skin cancer and pre-cancerous tumors of mouth, skin and eyes.


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, degenerative 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 vital for survival.


For the most complete and up-to-date coverage of this disease, please refer to this GeneReviews article. Xeroderma Pigmentosum


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.


For other information on XP, please visit these pages:


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