Association of acute urticaria with Mycoplasma pneumoniae infection in hospitalized children

Background: Acute urticaria is a common and disturbing disorder in children and has a versatile etiology. Objective: To investigate the association of acute urticaria with Mycoplasma pneumoniae infection in hospitalized children. Methods: Hospitalized children with acute urticaria from Taiwan who did not respond to antihistamine treatment and avoidance of food allergens were studied from February 1, 2006, to July 31, 2007. These patients with urticaria were compared with those who had other respiratory tract diseases and were classified into 2 groups: urticaria patients with and without M pneumoniae infection. The presence of M pneumoniae infection was determined by positive serologic findings. Results: Sixty-five patients with acute urticaria and 49 patients with other respiratory tract diseases were enrolled in this study. Patients with urticaria had significantly less febrile duration but significantly higher platelet and lymphocyte counts than those with other respiratory tract diseases. Of the 65 patients with urticaria, 21 (32%) showed serologic evidence of M pneumoniae infection. Patients with M pneumoniae-associated urticaria received azithromycin treatment and needed a shorter time for improvement (P = .01) and complete resolution (P = .04). The total IgE levels and the results of specific IgE tests were not significantly different between urticaria patients with and without M pneumoniae infection. Conclusion: This study found that in Taiwan one-third of acute childhood urticaria leading to patient hospitalization was related to M pneumoniae infection. Therefore, children with urticaria who are not responding to antihistamine treatment and abstinence from food allergens should be encouraged to undergo serologic examinations for M pneumoniae to diagnose this antibiotic-responsive disorder. Ann Allergy Asthma Immunol. 2009:103:134-139.