Investigation of the factors affecting the progression of acute spontaneous urticaria to chronic spontaneous urticaria in children

Urticaria is defined as acute spontaneous urticaria (ASU) if it lasts less than six weeks without a physical trigger and chronic spontaneous urticaria (CSU) if it lasts longer. These two conditions, which have the same clinical presentation but different duration, differ in terms of pathogenesis, triggers, and prognosis. There is limited data on why urticaria, which starts acutely in children, is limited to six weeks in some children and becomes chronic in others. In this study, we aimed to investigate the rate of CSU in children presenting with ASU, and the clinical and laboratory factors that may affect CSU. For this purpose, patients younger than 18 years of age who were admitted to Pamukkale University Pediatrics Outpatient Clinics and Pediatric Emergency Department between March 1, 2022, and March 1, 2023, with urticaria and diagnosed with ASU were included in the study. On admission, all demographic and clinical characteristics of the patients, as well as urticaria-related features such as duration and possible trigger of urticaria and urticaria activity score (UAS) were recorded. A blood sample was collected for the laboratory parameters that may be effective in the pathogenesis and prognosis of CSU. At the end of the first and sixth week after admission, the patients were questioned whether their urticaria persisted or not via telephone interviews. Patients with persistent urticaria were considered as CSU at the end of the sixth week. The clinical and laboratory characteristics at the presentation of the patients with CSU and ASU were compared. The median age and UAS value at the presentation of 211 (53% female) patients were 6.2 years (interquartile range 3.4-10.3) and 3 (interquartile range 2-4), respectively. At the end of the sixth week, 204 (96.7%) patients with a total duration of urticaria of fewer than six weeks were considered as ASU, and 7 (3.3%) patients with a total duration of urticaria of more than six weeks were considered as CSU. Urticaria activity score at admission was similar in the CSU and ASU groups. The frequency of antihistamine use (85.7% and 45.1%, respectively, p=0.034); the presence of previous urticaria history (71.4% and 19.1%, respectively, p=0.001); and the rate of concomitant physical urticaria (42.9% and 1%, respectively, p<0.001); the presence of urticaria on the seventh day (85.7% and 10.3%, respectively, p<0.001); anti-thyroglobulin autoantibody positivity (14.3% and 1%, respectively, p=0.004), anti-nuclear antibody (ANA) positivity (57.1% and 22.6%, respectively, p=0.035) were significantly higher in the CSU group than in the ASU group. Peripheral blood leukocyte count was significantly higher in the ASU group than in the CSU group (median 9840 and 7000/µL, respectively, p=0.021). Serum platelet-activating factor (PAF) (median 0.85 and 0.82 ng/mL, respectively, p=0.898) and interleukin-6 (IL-6) (median 8.53 and 5.31 IU/mL, respectively, p=0.451) levels were similar in both groups. Serum tryptase levels were higher in the ASU group than in the CSU group, but the difference was not statistically significant (median 4.1 and 2.7 µg/L, respectively, p=0.055). Multivariate logistic regression analysis showed that the most important factors affecting chronicity were the persistence of urticaria on the seventh day (OR: 71.7; 95% CI 4.31-1193.76, p=0.003) and previous urticaria history (OR: 39.5; 95% CI 1.70-920.21, p=0.022). In conclusion, to the best of our knowledge, our study is the first study in the literature to show the rate of CSU in children presenting with ASU, and this rate was found to be 3.3% in this study group. In addition, we found that a history of urticaria at any time before and the presence of urticaria on the seventh day of admission were the most important factors that affecting the progression of ASU to CSU in children. We hope that our study findings will be useful for clinicians in terms of closer follow-up of children with ASU who have high risk for CSU. Keywords: Urticaria, acute urticaria, chronic urticaria, urticaria activity score, tryptase, platelet-activating factor, interleukin-6.