Abstract
IMPORTANCE: Chronic urticaria (CU) affects 0.1% to 0.3% of children. Most cases have no identifiable trigger and are classified as chronic spontaneous urticaria (CSU). At least half of patients with CSU may have an autoimmune etiology that can be determined in vitro using the basophil activation test (BAT). While 30% to 55% of CU cases resolve spontaneously within 5 years in adults, the natural history and predictors of resolution in children are not known. OBJECTIVE: To assess the comorbidities, natural history of CU, and its subtypes in children and identify predictors of resolution. DESIGN, SETTING, AND PARTICIPANTS: We followed a pediatric cohort with chronic urticaria that presented with hives lasting at least 6 weeks between 2013 and 2015 at a single tertiary care referral center. EXPOSURES: Data were collected on disease activity, comorbidities, physical triggers, BAT results, complete blood cell count, C-reactive protein levels, thyroid-stimulating hormone levels, and thyroid peroxidase antibodies. MAIN OUTCOMES AND MEASURES: We assessed the rate of resolution (defined as absence of hives for at least 1 year with no treatment) and the association with clinical and laboratory markers. RESULTS: The cohort comprised 139 children younger than 18 years old. Thirty-one patients (20%) had inducible urticaria, most commonly cold induced. Six children had autoimmune comorbidity, such as thyroiditis and type 1 diabetes. Autoimmune disorders (24 patients [17%]) and CU (17 patients [12%]) were common in family members. Positive BAT results (CD63 levels > 1.8%) were found in 58% of patients. Patients with positive BAT results (CD63 level >1.8%) were twice as likely to resolve after 1 year compared with negative BAT results (hazard ratio [HR], 2.33; 95% CI, 1.08-5.05). In contrast, presence of basophils decreased the likelihood of resolution (HR, 0.40; 95% CI, 0.20-0.99). No correlation with age was found. Chronic urticaria resolved in 43 patients, with a rate of resolution of 10.3% per year. Levels of CD63 higher than 1.8% and absence of basophils were associated with earlier disease resolution. CONCLUSIONS AND RELEVANCE: Resolution rate in children with CU is low. The presence of certain biomarkers (positive BAT result and basophil count) may help to predict the likelihood of resolution.