Abstract: 【Abstract】 Objective To analyze the etiology of chronic spontaneous urticaria （CSU） in children and associated factors affecting the disease severity. Methods A single-center cross-sectional study was conducted. Children aged ≤ 17 years with CSU were prospectively enrolled at the Department of Dermatology, Children′s Hospital of Chongqing Medical University from November 2021 to November 2022. Clinical data were collected, serum total IgE and allergen-specific IgE （sIgE） were detected, and basophil activation test （BAT） and autologous serum skin test （ASST） were performed. According to the ASST and BAT results, the children were divided into the chronic autoimmune urticaria （CAU） group （positive for both ASST and BAT）, non-CAU group （negative for both ASST and BAT）, and partial CAU group （positive for either ASST or BAT）. Differences in the etiology and clinical characteristics were analyzed between the CAU group and the non-CAU group. Based on the weekly urticaria activity score （UAS7）, the children with CSU were divided into the mild group （UAS7 < 16 points） and moderate to severe group （UAS7 ≥ 16 points）. Factors associated with the severity of CSU in children were analyzed using logistic regression. Non-normally distributed quantitative data were expressed as M （Q1, Q3）, and the non-parametric rank sum test （Kruskal-Wallis test） was used to compare quantitative data among multiple groups. Results This study enrolled a total of 93 children with CSU, including 50 males （53.8%） and 43 females （46.2%）, with the age being 5.9 （2.9, 9.2） years, and the disease duration being 4 （2, 8） months; 32 patients （34.4%） were complicated by angioedema, 28 （30.1%） had a family history of chronic urticaria, 49 （52.7%） had a family history of atopic diseases, 14 （15.1%） had a family history of autoimmune diseases, and 26 （28.0%） had at least one atopic comorbidity. Etiologic analysis showed that 32 cases （32/69, 46.4%） were positive for ASST and 28 （28/70, 40.0%） were positive for BAT. Both ASST and BAT were performed in 57 cases, and they were divided into the CAU group （18 cases）, non-CAU group （24 cases）, and partial CAU group （15 cases） according to the test results. There were no significant differences in the age, disease duration, gender ratio, proportion of patients with atopic comorbidity, or proportion of patients having a family history of atopic diseases among the 3 groups （all P > 0.05）, while the proportion of patients with moderate to severe CSU （UAS7 ≥ 16 points） was higher in the CAU group （16/18） than in the non-CAU group （11/24, P < 0.05）. Triggering factors were identified in 19 cases （20.4%）, including 18 （19.3%） cases of food allergy and 1 case （1.0%） of antibiotic allergy. The serum total IgE level was elevated in 22 cases （22/89, 24.7%）, and 40 （40/81, 49.4%） showed elevated levels of at least 1 sIgE. The UAS7 of the children with CSU was 16 （15, 21） points, and there were 31 （33.3%） children with mild CSU and 62 （66.7%） with moderate to severe CSU. Univariate logistic regression analysis showed that BAT positivity was associated with disease severity （OR = 7.566，95% CI: 2.238 - 25.572，P < 0.05）. After adjustment for age and gender, multivariate logistic regression analysis showed that BAT positivity was associated with moderate to severe CSU （OR = 6.725, 95% CI: 1.361 - 33.227, P < 0.05）. Conclusions Autoimmunity may be the main cause of CSU in children, followed by allergic factors. ASST could be used as a primary screening test for the diagnosis of CAU in children, and BAT may help identify CAU and predict disease severity.

Key words: Urticaria, Child, Autoimmunity, Chronic spontaneous urticaria, Chronic autoimmune urticaria, Basophil activation test, Autologous serum skin test