Background: IgE and high-affinity IgE receptor (FcεRI) expression on basophils have been scarcely explored in patients with chronic inducible urticaria (CIndU). Objectives: To investigate baseline serum IgE and FcεRI expression on blood basophils in a large cohort of CIndU patients and its relationship to treatment response. Methods: Baseline total serum IgE and basophil FcεRI expression measured by flow cytometry in 165 patients with CIndU was studied. The relationship of both parameters with the response to antihistamine and anti-IgE (omalizumab) treatment was considered in a subsample of CIndU patients. FcεRI expression in basophils was assessed by mean fluorescence intensity (MFI) and basophil FcεRI standardized density (receptors/cell). Results:The median FcεRI expression standardized per density in blood basophils was found significantly higher in patients with CIndU compared to HCs. A positive correlation was found between IgE serum levels and basophil FcεRI expression.Basal FcεRI expression was not related to antihistamine treatment response.However, it was related to omalizumab, and patients responding to omalizumab showed higher basal basophil expression of FcεRI levels. Non-responders to the antihistamine showed significantly higher IgE serum levels.Conclusions: FcεRI receptor overexpression in patients with CIndU shows almost the same pattern than chronic spontaneous urticaria. It seems to be independent of CIndU subtypes. Although additional studies would be welcome, our work highlights the relevance of FcεRI receptor regulation in CIndU supporting autoimmune basophil and mast cell activation and may be a biomarker for response to anti-IgE therapy.

Purpose of review Urticaria is a frequent disorder that can present with erythema, edema, and pruritus involving the skin and mucous membranes. Early diagnosis and proper management of the urticaria according to the type (i.e., acute vs chronic) is of utmost importance to reduce the burden of the disease and prevent psychosocial comorbidities. In this review, we aim to summarize the diagnosis and management of acute and chronic urticaria with emphasis on the differences. Recent findings Autoimmune mechanisms (type I or type IIb autoimmunity) have been recently defined in the pathogenesis of chronic spontaneous urticaria. Despite the high rates of symptom control in both acute and chronic urticaria with the existing treatment options, new treatments are still needed in a subset of patients. Promising treatment targets in CSU include Bruton’s tyrosine kinase, Siglec-8, or IL-4/13. Summary Therapeutic management of acute and chronic urticaria is still challenging despite the highly effective treatments. In addition to symptomatic treatment, elicitation of the pathogenesis of both forms of urticaria and clear understanding of the nature of the disease by the patient are essential. Urticaria has still a high impact on the patients’ quality of life warranting the studies on the pathogenesis, novel treatment options, and the factors determining which patients with acute urticaria will likely develop chronic urticaria.