Xeroderma pigmentosum

Xeroderma pigmentosum is a genetic disorder of DNA repair in which the body's normal ability to fix mutations caused by UV light is disabled. This leads to multiple basaliomas and other skin malignancies at a young age. Therefore in very severe cases it is necessary to avoid all sunlight. more...

Types

There are eight types.

• Dominant Type (OMIM 194400)
• Type A, I, XPA, Classical Form (OMIM 278700)
• Type B, II, XPB (OMIM 133510)
• Type C, III, XPC (OMIM 278720)
• Type D, IV, XPD (OMIM 278730)
• Type E, V, XPE (OMIM 278740)
• Type F, VI, XPF (OMIM 278760)
• Type G, VII, XPG (OMIM 278780)

Causes

Damage to DNA is a frequent occurrence, and the body has mechanisms to fix it by cutting out the damaged segment and replacing the resulting gap in the DNA with the correct base pairs from the opposing strand ("nucleotide excision repair"). The enzymes DNA polymerase and ligase fulfil this role. The most common defect in xeroderma pigmentosum is an inherited defect that alters the nucleotide excision repair enzymes, and hinders their functionality. Therefore, DNA damage is not readily fixed.

Treatment

The most important part of managing the condition is reducing exposure to the sun.

The number of keratoses can be reduced with Isotretinoin () (though there are significant side-effects.) Existing keratoses can be treated using cryotherapy or fluorouracil. ().

In popular culture

A notable fictional character who sufferers XP is Christopher Snow featured in the novels Fear Nothing and Seize the Night by Dean R. Koontz.

The film The Others features characters who suffer from XP.

Late in 2005, ABC's Extreme Makeover: Home Edition gave kids with XP a once in a lifetime opportunity, a night at Disney World. Disney World opened for a night just for kids with XP. Footage from this event aired as part of an Extreme Makeover holiday special on December 11, 2005.

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