Disorders of nucleotide excision repair.

Deficient repair of ubiquitous errors in the genome risks faulty transcription or replication. Its direct and indirect phenotypic consequences are rare, complex, dementing, lethal disorders of children with inadequately understood overlapping genotypes and variable severity. Mutations of CSA or CSB responsible for impaired transcription-coupled repair cause Cockayne syndrome (CS). Its characteristics are (1) profound growth deficiency affecting all tissues, including the brain, (2) premature aging marked by cachexia, vascular disease, exocrine deficiency, and osteopenia, but not cancer, and (3) a selective degenerative disorder of central and peripheral myelin and by neuronal loss in the retina and inner ear, and in the cerebellum and basal ganglia where it is associated with calcification. Xeroderma pigmentosum (XP) can arise from mutations of at least eight genes involved in global genomic repair. Severe XPA and XPC cause innumerable carcinomas and melanomas in light-exposed eyes and skin, and enhanced risk of visceral cancers. XPA and XPD and others can cause childhood XP neurological disease with widespread neuronal loss, axonal sensorimotor neuropathy, and dwarfing. Four genes, including XPD, can cause trichothiodystrophy (TTD) with sulfur-deficient, brittle, tiger-tail hair, and growth and developmental inadequacy. CSB or XPD can cause the severe congenital cerebro-oculofacioskeletal (COFS) CS-like syndrome with joint contractures, cataracts, and early death. Three XP genes can also cause XP/CS complex. Much more needs to be learned about these and other disorders of DNA repair to enable prevention and treatment.