Characteristics and clinical significance of augmentation spectra in solar urticaria

Abstract

Solar urticaria has unique spectra, such as inhibition and augmentation. The clinical significance of these spectra, especially augmentation, is not well understood. Reported cases of solar urticaria with augmentation spectra are extremely rare in the published English‐language work. The purposes of this study were to evaluate the clinical features of solar urticaria with augmentation spectra and to elucidate the mechanisms and clinical importance of the spectra. We experienced 11 cases (five females, six males; mean age, 40.1 years; range, 1–74) of solar urticaria with augmentation spectra from April 2007 to July 2019. Augmentation spectra were UV‐B in three cases, UV‐A in two, visible light in four, UV‐A and UV‐B in one, and UV‐A and visible light in one. Augmentation spectra were observed before action spectra in four cases, after in six, and before and after in one. Injection of sera irradiated with action spectra and augmentation spectra in vitro induced stronger immediate reactions than those of only action spectrum‐irradiated sera in four of five cases. The results of injection tests suggested that augmentation spectra enhance the production of urticaria‐forming factor. Clinically, we observed severe urticarial reactions in four cases, including anaphylaxis in three and moderate urticarial reactions in three. These results suggest that augmentation spectra are not as rare as previously thought and that they are associated with the severity of solar urticaria. Therefore, phototesting for both augmentation and action spectra should be performed to provide appropriate guidance for patients with solar urticaria.

Pathogenesis of solar urticaria: Classic perspectives and emerging concepts

“…The SU action spectrum is relatively distinct amongst photodermatoses, as it can vary radically between patients and extend across the entire UV spectrum, although a majority of patients are sensitive to either the UVA or visible light wavebands. 3,6,9,[23][24][25] From a photobiologic perspective, this accords with in vitro activation experiments, where autologous injection of serum fractions containing proteins of vastly divergent molecular weights successfully elicited SU symptoms in several patients. 20 Unfortunately, analysis of action spectra has not resulted in the identification of putative chromophores that produce mast cell activation in SU.…”

“…Since the development of phototesting in 1953, 22 it has become possible to define more precisely the action spectrum for SU patients and to gain insights into its causal chromophores. The SU action spectrum is relatively distinct amongst photodermatoses, as it can vary radically between patients and extend across the entire UV spectrum, although a majority of patients are sensitive to either the UVA or visible light wavebands 3,6,9,23‐25 . From a photobiologic perspective, this accords with in vitro activation experiments, where autologous injection of serum fractions containing proteins of vastly divergent molecular weights successfully elicited SU symptoms in several patients 20 .…”

“…This discrepancy suggests a number of possibilities: (1) that some individuals are provoked by a wavelength simply not included in current phototesting protocols; (2) that interaction of multiple wavelengths with their respective chromophores is required to provoke SU in certain individuals and; (3) that interaction of solar electromagnetic radiation and other physical or non‐physical stimuli may be required to provoke SU in specific cases. Certainly, a requirement for interaction of multiple wavelengths in the provocation of SU is supported by observations of both augmentation and inhibition spectra, whereby pre‐ or post‐irradiation of skin with specific wavelengths increases or decreases urticarial responses, respectively 24,27 . Furthermore, the notion that more than one type of stimulus may be required to provoke SU is suggested by the frequent co‐occurrence of SU and other forms of chronic urticaria (in up to 16% of cases), 9 as well as reports from other forms of chronic inducible urticaria wherein weals only develop in the presence of several concomitant physical stimuli 28 …”

“…Certainly, a requirement for interaction of multiple wavelengths in the provocation of SU is supported by observations of both augmentation and inhibition spectra, whereby pre-or post-irradiation of skin with specific wavelengths increases or decreases urticarial responses, respectively. 24,27 Furthermore, the notion that more than one type of stimulus may be required to provoke SU is suggested by the frequent co-occurrence of SU and other forms of chronic urticaria (in up to 16% of cases), 9 as well as reports from other forms of chronic inducible urticaria wherein weals only develop in the presence of several concomitant physical stimuli. 28 Further complexity emerges when one considers the observation that action spectra in SU can demonstrate temporal evolution.…”