Loss of Function Variants in the XPC Causes Severe Xeroderma Pigmentosum in Three Large Consanguineous Families.

Background: Xeroderma pigmentosum (XP) is a rare recessively inherited disorder that presents clinical and genetic heterogeneity. Mutations in eight genes, of which seven are involved in nucleotide excision repair (NER) pathway have been reported to cause the XP.

Methods And Results: Three large consanguineous families of Pakistani origin displaying typical clinical hallmarks of XP were evaluated at clinical and molecular level. Homozygosity mapping using microsatellite markers established linkage of the families to XPC gene on chromosome 3p25.1. Sanger sequencing of the XPC gene identified a novel homozygous single bp deletion [NM_004628.5; c.1934del; p.(Pro645Leufs*5)] and two previously reported mutations that included a nonsense [c.1243 C>T; p.(Arg415*)] and a splice acceptor site (c.2251-1 G>C), all segregating with the disease phenotypes in the families.

Conclusion: This report has extended the spectrum of mutations in the XPC gene and will also facilitate in diagnosis of XP and counselling of families inheriting it, which is the only inevitable tool for preventing the disease occurrence in future generations.