PD05 Chronic actinic dermatitis: a multicentre evaluation

Abstract Chronic actinic dermatitis (CAD) is a chronic photosensitivity disorder typically characterized by an eczematous eruption on photoexposed sites. Diagnosis relies on specialist phototesting, but there is no consensus on formal diagnostic criteria. As part of the efforts by the British Photodermatology Group to develop a set of diagnostic criteria for CAD, this study was undertaken to gain a deeper understanding of the clinical and photobiological disease characteristics of CAD in the UK. A retrospective review of medical records and in-house databases was undertaken for 5–25 patients diagnosed with CAD at each of six photobiology units in the UK. Data collected included patient demographics, disease characteristics and investigation findings. Data were available for 93 patients with CAD; 51% were male. The median age at diagnosis was 44 years (range 8–85), and the median age of photosensitivity onset was 33 years (range 4–80). Skin phototypes (SPTs) were I–IV in 62%, V–VI in 33%, and unrecorded in 4% of patients. Patients with SPT I–IV were predominantly male (59%), while those with SPT V–VI were mainly female (61%). The duration of sunlight exposure required to provoke symptoms was < 1 h in 59% of cases, and perennial symptoms were noted in 52%. Concurrent atopic diseases were common, with 46% having atopic dermatitis, 40% asthma, 46% hay fever and 53% elevated IgE levels. Only 32 (34%) patients were vitamin D sufficient, including 12 taking oral supplements. Monochromator phototesting revealed reduced minimal erythema doses (MEDs) in ultraviolet (UV)B wavebands (300–305 nm) in 83–84% of cases, mid-UVA (350–365 nm) in 70–74%, and longer UVA (380–400 nm) in 11–19%. Notably, the greatest reductions in MED occurred at 300 nm (28% of the lowest normal range). Broadband provocation testing was conducted in 77% of cases, with 81% showing abnormal reactions to broadband UVA and 94% to solar simulated radiation. Most patients who were patch or photopatch tested had positive reactions, with only 29% testing negative. In this national dataset, CAD was found to affect people with a wide range of ages and skin phototypes, and atopic disease and vitamin D deficiency were common. Patients with CAD exhibit significant photosensitivity, with flare-ups triggered by brief UV exposure. Phototesting plays a crucial role in identifying the disease’s action spectrum, revealing typically broad-spectrum UV waveband involvement, with marked UVB sensitivity and often also UVA involvement. These data help to further characterize this challenging condition and provide important insights, which will facilitate consensus practices in photodiagnosis.