OBSOLETE: Xeroderma pigmentosum complementation group C

Xeroderma pigmentosum complementation group C (XP-C) is a rare autosomal recessive disorder caused by mutations in the XPC gene, which encodes a protein essential for global genome nucleotide excision repair (GG-NER). This DNA repair pathway is responsible for recognizing and removing ultraviolet (UV)-induced DNA damage, particularly in non-transcribed regions of the genome. XP-C is one of the most common complementation groups of xeroderma pigmentosum, particularly prevalent in North Africa and the Middle East. Patients with XP-C typically present in early childhood with extreme sensitivity to sunlight, leading to severe sunburns, freckling, and progressive skin changes in sun-exposed areas. The skin is the most prominently affected organ system, with patients developing premature photoaging, actinic keratoses, and a dramatically elevated risk of skin cancers including basal cell carcinoma, squamous cell carcinoma, and melanoma, often occurring before age 10. Unlike some other XP complementation groups, XP-C patients generally do not develop the progressive neurological degeneration seen in groups such as XP-A or XP-D, though some neurological involvement has occasionally been reported. The eyes may also be affected, with photophobia, conjunctival inflammation, and ocular surface neoplasms. Note: Orphanet code 276255 is listed as OBSOLETE, meaning this entry has been retired or merged into a broader classification. Patients and clinicians should refer to the current Orphanet entry for xeroderma pigmentosum complementation group C (Orphanet: 154) for up-to-date information. There is currently no cure for XP-C. Management centers on rigorous UV protection including protective clothing, UV-filtering eyewear, and avoidance of sun exposure. Regular dermatological surveillance for early detection and removal of skin cancers is critical. Topical treatments such as 5-fluorouracil or imiquimod may be used for precancerous lesions. Research into gene therapy and pharmacological approaches is ongoing but remains experimental.

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