PD04 Real-life experience of Scottish patients with idiopathic solar urticaria

Abstract

Abstract We conducted a retrospective study to characterize our most recent cohort of patients with idiopathic solar urticaria (SU), to compare with our previous findings (Beattie PE, Dawe RS, Ibbotson SH, Ferguson J. Characteristics and prognosis of idiopathic solar urticaria: a cohort of 87 cases. Arch Dermatol 2003; 139:1149–54). We analysed data derived from our in-house database and paper and electronic records of patients with SU seen through the Scottish Photobiology Service between 2003 and 2022. Eighty-four patients with SU were seen in this period, 57 (68%) women and 27 (32%) men. Twenty-nine (35%) had a single consultation/phototesting and 55 (65%) had follow-up assessments. The average age of onset was 37 years, with the average age of diagnosis being 41 years, with delays from symptom onset to diagnosis ranging from 6 months to 24 years. Importantly, 20 (24%) patients self-reported systemic symptoms, most commonly fatigue, dizziness and nausea. Of 61 patients using antihistamines before diagnosis, 31 (51%) reported benefit. Of patients who tried sunscreens, 31 of 65 (48%) reported benefit. On monochromator phototesting, sensitivity predominantly involved the ultraviolet (UV)A waveband (335–400 + 27 nm in 55%), extending into the visible spectrum (> 430 + 27 nm) in 44% and UVB waveband (305 + 5 nm) in 1%, consistent with previous reports of predominant UVA/visible light dependency in SU. On review of follow-up data, we analysed the fold benefit in minimal urticaria dose (MUD) from testing on H1 antihistamines alone, H1 and H2 antihistamines combined and the addition of montelukast. Most (65%) responded with a more than twofold improvement in MUD after a single dose of H1 antihistamine, with only 35% not responding. Increasing the dose of H1 antihistamine did not provide notable additional benefit. There was a suggestion of improved responses by the addition of an H2 antagonist (in 76% vs. 66% with H1 antagonist alone), but this was not statistically significant (P > 0.05). No additional improvement in threshold sensitivity (MUD) was observed by the addition of montelukast. Small numbers of patients used other treatments such as photo(chemo)therapies and systemic immunosuppressants, and these were found to be of limited benefit. Since 2011, we have used omalizumab for patients with treatment-resistant SU. Of the current cohort, 13 received omalizumab, with 62% reporting a good clinical response and a further 15% a partial clinical response. Phototesting in these patients showed complete abolition of photosensitivity or excellent responses (more than fivefold increase in MUD) in 73%, demonstrating the efficacy of omalizumab in recalcitrant SU. Given the systemic features reported by some patients with SU, this supports a management approach, which includes systemic immunomodulation as a potentially effective option.