Xeroderma pigmentosum is an autosomal recessive disorder characterized by sun sensitivity and increased skin sensitivity to UV light, as well as an increased risk of skin cancer associated with a defect in nucleotide excision repair (NER). The XPF form of XP is usually relatively mild compared to other forms. Patients with XPF tend to have later onset of skin cancer. Some patients with XPF may develop neurologic impairment or growth defects, and are then classified as having Cockayne syndrome. [From OMIM]