Few studies have examined photoprotection practices in individuals with rare genetic diseases, such as Xeroderma Pigmentosum (XP), where photoprotection is an important aspect of managing the condition. Currently no validated self-report tool exists for assessing adherence. Aims: We sought to validate a self-reported measure of adherence to face photoprotection behaviours in individuals diagnosed with XP. Methods: 66 XP patients recruited from the patient list of the XP specialist service in

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... don, UK, completed a survey including self-reported adherence to specific photoprotection behaviours and wore a wrist-worn UVR electronic dosimeter for 21 days while also completing a daily UVR photoprotection diary. Internal reliability and convergent validity of the measure was explored in relation to self-reported UVR photoprotection practices, clinical variables, and objective measures of UVR protection. Results: Internal consistency of the self-reported scale was satisfactory. Correlations between the adherence to photoprotection measure with other photoprotection practices and clinical variables ranged from small to large in size. There was general agreement between the self-reported measure and diary and dosimeter measures as the mean scores for levels of adherence to photoprotection increased with average day protection. However, there were outliers specifically at the higher ends of average day protection and poor agreement between levels of adherence to the face photoprotection and the amount of UVR dose reaching the face. Conclusions: Findings showed that our measure may provide a standardised and internally reliable self-reported assessment of UVR protection. However, given the potential low sensitivity to detect high adherence, we encourage future studies to combine objective and subjective reports to increase the confidence in the accuracy of the measure of adherence to face photoprotection.