ABSTRACT
Patients suffering from Xeroderma pigmentosum (XP), trichothiodystrophy (TTD), and Cockayne syndrome (CS) are defective in the process of nucleotide excision repair (NER). Neurological changes in XP include microcephaly and are usually progressive and comprise reduction of deep tendon reflexes, peripheral neuropathy and loss of intellectual function. CS patients often have microcephaly, lack of myelination, and may have calcification of basal ganglia as well as other parts of the brain. All XP patients are highly susceptible to development of sunlight-induced cancers of the skin and eyes. In some parts of North Africa, XP is more common and children with tumors of the tip of the tongue should be considered as having XP until proven otherwise. Complementation analysis revealed the presence of seven XP-subtypes, deficient in NER as well as a variant form with a deficiency in Deoxyribonucleic acid (DNA) polymerase eta. XP has to be distinguished from the other DNA repair deficient photodermatoses such as CS and TTD.
