PD04 Shining a light on eczema: a prospective, comparative, cohort study of dupilumab and Janus kinase inhibitors in photosensitive atopic dermatitis

Abstract Photosensitive atopic dermatitis (PSAD) is a rare eczema variant exacerbated by ultraviolet radiation, presenting significant treatment challenges. Dupilumab, which targets interleukin-4 and interleukin-13, and Janus kinase (JAK)2 inhibitors, which modulate cytokine signalling, are emerging as potential therapies. This study evaluates the efficacy of dupilumab and JAK2 inhibitors in patients with severe PSAD, assessing ultraviolet radiation erythemal thresholds, eczema severity scores, and quality of life (Dermatology Life Quality Index: DLQI). This prospective, comparative cohort study included 11 patients: six treated with dupilumab and five with JAK2 inhibitors, with one patient transitioning between therapies. Patients underwent monochromator light testing to measure erythemal thresholds across 300–600-nm wavelengths, alongside assessments using DLQI, Eczema Area and Severity Index (EASI) and Patient-Oriented Eczema Measure (POEM). Both treatment groups showed improvement in phototesting thresholds, particularly in the ultraviolet B range (300–400 nm). The JAK2 cohort demonstrated a significant improvement in mean phototesting thresholds from 20 J cm−2 to 40 J cm−2 at 300 nm, while those receiving dupilumab showed a smaller increase from 20 J cm−2 to 28 J cm−2. At 320 nm, JAK2 thresholds improved from 2.5 to 4 J cm−2, and dupilumab from 1 to 2 J cm−2. At 330 nm, patients in the JAK2 group significantly improved from 3.5 to 14 J cm−2, whereas those receiving dupilumab declined from 10 to 7 J cm−2. At 370 nm, patients receiving JAK2 inhibitors improved from 20 to 28 J cm−2, while the dupilumab group remained unchanged. Notably, at 400 nm, patients in the JAK2 cohort had improved thresholds from 57 to 113 J cm−2. In terms of quality of life, patients receiving dupilumab had a mean EASI of 26.3 and a POEM of 15.2 pretreatment, achieving 77% improvement. The JAK2 cohort had a mean EASI of 36.1 and POEM of 13.0 pretreatment, achieving 75% improvement. DLQI scores of patients in the JAK2 group showed an 84.2% reduction, improving from 18.25 to 3.5, compared with dupilumab’s 77% improvement from 19.0 to 6.0. In conclusion, JAK inhibitors demonstrate superior efficacy compared with dupilumab in improving photosensitivity, as indicated by increased monochromator light testing thresholds and reduced DLQI scores. While dupilumab effectively reduces flare intensity and itch severity, its effect on photosensitivity is minimal. These results highlight the need for larger studies to further validate these findings and refine PSAD treatment strategies.