Measuring ultraviolet exposure to the face in patients with xeroderma pigmentosum

Xeroderma pigmentosum (XP) is a genetic disease in which the system that repairs damage caused by ultraviolet (UV) radiation (which mainly comes from the sun) is faulty. As a result, patients with XP develop eye and skin cancers from childhood and usually die in early adulthood. In this paper, with authors from the UK, the Netherlands and Denmark, a new method was used to estimate face exposure in 36 patients with XP over 3 weeks in the summer. Some patients with XP protected themselves well, whereas others did not. The difference between the face UV dose in the best and worst protecting patients was over 100‐fold. Those patients protecting themselves the least from UV exposure had exposure levels similar to healthy adults. Adults and children with XP had similar exposure to UV but achieved it differently. Adults protected less well when outside but went outside less whereas children went outside more but protected better. This variation in UV exposure is important. As well as being useful in XP, this new method to estimate facial UV exposure may also be useful in other more common diseases, particularly patients at high risk of basal and squamous cell carcinomas, which are mostly caused by UV and mainly affect the face.