PD03 Drug-induced photosensitivity: a 10-year review from a tertiary photodiagnostic service

Abstract

We aimed to characterize the clinical features, phototesting findings and implicated drugs among patients with suspected drug photosensitivity. Patients were recruited at a referral or initial specialist assessment at a tertiary photodiagnostic service between 2014 and 2024. A retrospective review of an in-house photodiagnostic database and clinical records was undertaken, with Caldicott Guardian approval (IGTCAL-2024-409). Demo­graphic and clinical data, suspected culprit drugs and photodiagnostic findings were analysed, with diagnosis based on clinical assessment, drug history, response to withdrawal and phototesting. During the study period, 2535 patients attended, 54 (2%) with suspected drug photosensitivity. Following assessment, drug-induced photosensitivity was the primary diagnosis in 34 (63%), contributory in 15 and excluded in 5. Among primary or contributory cases (n = 49), 57% of patients (n = 28) were female, median age 58 years (range 25–85). Where recorded, 76% had phototypes I–II. Monochromator phototesting showed reduced erythemal thresholds in 33 patients (67%): 45% ultraviolet (UV)A alone, 27% UVA and visible, 18% UVA and UVB, and 9.1% visible alone. Where phototesting was normal or not performed, this reflected drug discontinuation before phototesting, lack of photo­testing or strong clinical suspicion despite normal phototesting. Among primary cases (n = 34), phototoxic reactions predominated (82%), with pseudoporphyria (9%), drug-induced lupus (6%) and solar urticaria (3%). Implicated drugs included diuretics (14%, mainly thiazides), statins (12%), immunomodulatory agents (12%), nonsteroidal anti-inflammatory drugs (12%), quinine (8%), oncological therapies (8%), antihypertensives (8%), antimicrobials (6%), proton-pump inhibitors (6%), anti­fibrotics (4%), antiepileptics (4%) and other agents (4%). The median latency from drug commencement to symptom onset was 24 months (range ∼1 day to 30 years; n = 39). Drug-induced photosensitivity accounted for a small but significant proportion of referrals. Emerging drugs were implicated, including oncological and antifibrotic therapies. Although phototesting showed UVA-predominant sensitivity, normal testing did not exclude drug causality, emphasizing clinical correlation. Clinicians should not be falsely reassured by prolonged drug exposure prior to symptom onset – clinical assessment and, where feasible, phototesting are essential.