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xeroderma pigmentosum, VARIANT type (XPV)

Xeroderma pigmentosum is an autosomal recessive pigmentary skin disorder characterized by solar hypersensitivity of the skin, high predisposition for developing cancers on areas exposed to sunlight and, in some cases, neurological abnormalities. Some XP-D patients present features of Cockayne syndrome, including dwarfism, sensorineural deafness, microcephaly, mental retardation, pigmentary retinopathy, ataxia, decreased nerve conduction velocities.

The variant form of xeroderma pigmentosum (XPV) is caused by mutations in the DNA polymerase eta gene (POLH; 603968).
This XP 'variant' class is characterized by a defect in conversion of newly synthesized DNA from low to high molecular weight after UV irradiation (Masutani et al., 1999).
So-called 'pigmentary xerodermoid' is apparently identical to the XP variant, which is characterized by loss of a gene product that permits normal cells to replicate DNA without interruption at UV-damaged sites (Cleaver et al., 1980).
XPV shows normal nucleotide excision repair, but an exaggerated delay in recovery of replicative DNA synthesis. Most XPV patients do not develop clinical symptoms and skin neoplasias until a later age. Clinical manifestations are limited to photo-induced deterioration of the skin and eyes. 

ABREVIATION(S):
XPV
XP-V

TYPE: skin problem

Related patway(s): Fanconi anemia (FA) pathway, translesion synthesis (TLS)

DNAtraffic protein(s) related to disease: POLη (POLH /RAD30A)

OMIM: 278750

Last modification date: Aug. 17, 2011