OBSOLETE: Xeroderma pigmentosum complementation group B

Xeroderma pigmentosum complementation group B (XP-B) is an extremely rare autosomal recessive disorder caused by mutations in the ERCC3 (XPB) gene, which encodes a DNA helicase essential for nucleotide excision repair (NER) and transcription. This Orphanet entry (276252) is marked as OBSOLETE, meaning it has been reclassified or merged into other clinical entities. Mutations in the ERCC3/XPB gene can give rise to a spectrum of overlapping phenotypes, including xeroderma pigmentosum (XP), XP combined with Cockayne syndrome (XP/CS), and trichothiodystrophy (TTD). Because of this phenotypic variability, the complementation group B designation has been reorganized under these broader diagnostic categories rather than maintained as a standalone entity. Classically, patients with XP-B-related disease present with extreme sensitivity to ultraviolet (UV) radiation, leading to severe sunburn reactions, freckling, and a markedly increased risk of skin cancers at a young age. The skin, eyes, and nervous system are the primary body systems affected. Ocular manifestations include photophobia, keratitis, and potential corneal opacification. Progressive neurological degeneration, including sensorineural hearing loss, cognitive decline, and peripheral neuropathy, may occur, particularly in patients with combined XP/CS features. Some patients also exhibit growth failure and characteristic facial features associated with Cockayne syndrome. There is no cure for XP-B-related conditions. Management is centered on rigorous UV protection, including avoidance of sunlight, use of protective clothing, UV-filtering eyewear, and regular dermatologic surveillance for early detection and treatment of skin cancers. Neurological and developmental complications require multidisciplinary supportive care. Patients should be referred to specialized centers experienced in managing DNA repair disorders for optimal long-term follow-up.

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