What is xeroderma pigmentosum?

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An inherited genetic disease characterized by sensitivity to ultraviolet light.
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Related conditions: Skin cancer, eyelid tumors, telangiectasia, photophobia, mental retardation

Definition: Xeroderma pigmentosum is an inherited genetic disease characterized by extreme sensitivity to ultraviolet (UV) radiation. Patients with this disease have an extremely high risk of developing skin cancer and often die from skin cancer at an early age. Different classes of xeroderma pigmentosum have greater or lesser risks due to the severity of their disease. Dark skin color does not protect xeroderma pigmentosum patients from skin cancer.

Risk factors: The main risk factor for xeroderma pigmentosum is having a family member with the disease.

Etiology and the disease process: Xeroderma pigmentosum is caused by the lack of functionality of genes responsible for DNA repair after damage caused by ultraviolet light. The disease is classified as XPA, XPB (ERCC3), XPC, XPD (ERCC2), XPE (DDB2), XPF (ERCC4), XPG (ERCC5), or ERCC1 depending on which of seven genes involved in nucleotide excision repair (DNA repair) are damaged. XP-variant (XPV, or POLH) is a class for xeroderma pigmentosum patients who have a mutated DNA polymerase eta gene. Xeroderma pigmentosum is an autosomal recessive genetic trait. The disease is staged as follows:

  • Stage I: After six months of age, freckling, redness, and pigment changes appear on the skin.
  • Stage II: Patches of light and dark skin (poikiloderma) develop, and spider veins (telangiectasia) develop.
  • Stage III: Malignant skin cancers develop, including eyelid tumors.

Incidence: In the United States, xeroderma pigmentosum occurs in one in one million people. In the Japanese population the condition is more common, occurring in about one in twenty-two thousand people. A higher prevalence has also been noted in North Africa and the Middle East.

Symptoms: Common symptoms in xeroderma pigmentosum are freckling, changes in skin pigmentation such as poikiloderma, dry skin (xerosis), and the eventual development of multiple, malignant skin cancers. The eyelids may form papillomas or become atrophied, leading to deformity or the need for removal. Patients are sensitive to light, tend to suffer from conjunctival inflammation, and sunburn easily. Some patients exhibit immunosuppression and neurological problems such as learning disabilities, hearing loss, or degeneration of muscles and reflexes, especially in XPA and XPD. The intensity of symptoms varies by xeroderma pigmentosum class and exposure to ultraviolet light.

Screening and diagnosis: Clinical symptoms, often apparent within a year of birth, and family history are the first clues to xeroderma pigmentosum. Gene sequencing and other special tests are used to conclusively diagnose the disorder.

Treatment and therapy: Avoiding exposure to ultraviolet light, using sunscreen, and aggressive monitoring for skin cancer are necessary. Patients frequently require surgery or other treatment for skin cancer. Cases involving significant damage to eyelids may be treated with special eye drops or contact lenses to protect and moisturize the eyes.

Prognosis, prevention, and outcomes: Because xeroderma pigmentosum is an inherited genetic disease, genetic counseling is encouraged for those with a family history of the disorder before having children. Extreme measures are needed to protect the xeroderma pigmentosum patient from ultraviolet light from the sun or fluorescent lamps. Death from skin cancer is the typical outcome, usually by early adulthood.

Bibliography

Berman, Kevin. "Xeroderma Pigmentosum." MedlinePlus. Natl. Lib. of Medicine, Natl. Institutes of Health, 15 May 2013. Web. 9 Jan. 2015.

Hartree, Naomi. "Xeroderma Pigmentosum." Patient.co.uk. Egton Medical Information Systems, 18 March 2011. Web. 9 Jan. 2015.

Levy, Moise L., and Bruce H. Thiers. Pediatric Dermatology. Philadelphia: Saunders, 2013. Print.

"Xeroderma Pigmentosum." Cancer.net. American Soc. of Clinical Oncology, Jan. 2012. Web. 9 Jan. 2015.

"Xeroderma Pigmentosum." Genetics Home Reference. Natl. Lib of Medicine, Natl. Institutes of Health, 5 Jan. 2015. Web. 9 Jan. 2015.

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