Eosinophil Extracellular Traps in the Casts of Plastic Bronchitis Associated With Influenza Virus Infection

Plastic bronchitis (PB) is a rare pulmonary disease characterized by production of cohesive and branching casts that fill the airway. 1 Rubin B.K. Plastic bronchitis. Clin Chest Med. 2016; 37: 405-408 Abstract Full Text Full Text PDF PubMed Scopus (42) Google Scholar PB is classified into two types based on differences in the mechanism of development. Lymphatic PB, sometimes called “classic,” is associated mainly with congenital heart diseases or lymphatic anomalies, in the development of which aberrant pulmonary lymphatics appear to play a major role. Nonlymphatic PB is associated mainly with respiratory diseases, in which inflammatory immune cells may play a role. We and others have reported that influenza A (H1N1) pdm09 virus infection causes PB, especially in patients with an allergy and/or asthma. 2 Uda K. Shoji K. Koyama-Wakai C. et al. Clinical characteristics of influenza virus-induced lower respiratory infection during the 2015 to 2016 season. J Infect Chemother. 2018; 24: 407-413 Abstract Full Text Full Text PDF PubMed Scopus (6) Google Scholar ,3 Uchimura T. Mori M. Nariai A. Yokota S. Analysis of cases of severe respiratory failure in children with influenza (H1N1) 2009 infection in Japan. J Infect Chemother. 2012; 18: 59-65 Abstract Full Text PDF PubMed Scopus (10) Google Scholar Casts from some patients with PB due to influenza virus infection (Flu-PB) were composed of fibrin and such inflammatory immune cells as eosinophils and neutrophils. 4 Deng J. Zheng Y. Li C. Ma Z. Wang H. Rubin B.K. Plastic bronchitis in three children associated with 2009 influenza A(H1N1) virus infection. Chest. 2010; 138: 1486-1488 Abstract Full Text Full Text PDF PubMed Scopus (36) Google Scholar These findings indicate that granulocytes, as well as an allergic status, are likely to be involved in the pathophysiologic condition of Flu-PB. However, the detailed mechanisms of how highly viscous casts are formed in patients with Flu-PB and the roles of granulocytes remain unclear.