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Background: The pathogenesis of chronic spontaneous urticaria (CSU) is stillinsufficiently understood. Recentfindings suggest that immunoglobulins, in particularIgE but also IgA, play a role in the development of CSU.

Objective: Our aim was to assess differences in clinical and laboratory markers betweenCSU patients with and without lower levels of serum IgA and IgE.

Methods: We analyzed the data of 606 patients with CSU by dividing them into fourgroups based on their IgA and IgE levels. The groups were compared for their spectrum ofsymptoms, disease activity, concomitant autoimmunity and routine laboratory markers.Autoreactivity was assessed by basophil activation test (BAT). Moreover, IgE-anti-thyroidperoxidase (TPO) was measured.

Results:Of the patients with lower IgE levels, 66.5% also had lower IgA levels (r=0.316,p<0.001). Patients with lower IgA and lower IgE levels showed a higher prevalence ofrecurrent angioedema (p=0.03, p=0.04) and concomitant autoimmunity (p=0.006,p<0.001). Autoreactivity was also found more frequently in patients with lower IgA andlower IgE levels (p=0.003, p<0.001). Reduced basophil counts were linked to both, lowerIgA and lower IgE levels (p<0.001), whereas low eosinophil counts were primarily presentin patients with lower IgE levels (p=0.04, p<0.001). Patients with elevated IgE-anti-TPOlevels had lower IgA (p=0.007) and IgE levels (p=0.001).

Conclusion: Lower IgA levels in CSU are linked to lower IgE levels and features ofautoimmune urticaria. Ourfindings encourage to screen CSU patients for serum IgA andIgE levels and to further assess their role as disease biomarkers.