Summary
Xeroderma pigmentosum (XP) is a photodermatosis characterised by cutaneous hyperpigmentation arising in sun-exposed regions of the body during the first months of life. XP is a rare disease in the USA and Europe but the incidence is greater in regions with a high degree of consanguinity. The frequency of transformation of the lesions into tumours is significantly higher in XP patients than in the general population. Other clinical manifestations, such as neuropathy and developmental anomalies, may also be present. The disease is genetic and transmitted as an autosomal recessive trait. The primary genetic defect involves the process of DNA repair following exposure to ultraviolet (UV) radiation from the sun. This defect manifests as cellular hypersensitivity to UV rays and a reduced level of repair synthesis. To date, eight genes have been identified for the classic forms of XP together with another group referred to as xeroderma pigmentosum variants. The symptoms present, as well as their age of onset and severity, vary according to the gene involved. *Author: Orphanet (September 2002)*.
