Uncommon causes of chronic cough associated with airway eosinophilia

TLDR: The possible uncommon causes of chronic cough associated with airway eosinophilia, management of these uncommon causes, mechanistic insights linking eosInophilic airway inflammation and cough and management of eos inophilic infiltrates in the airways are described are described.

Abstract: J Thorac Dis 2021;13(5):3191-3196 | http://dx.doi.org/10.21037/jtd-20-2324 Chronic cough is defined as the sole or predominant symptom and lasting for more than 8 weeks, with a normal chest X-ray (1). The four common causes of chronic cough are cough-variant asthma (CVA), non-asthmatic eosinophilic bronchitis (NAEB), upper airway cough syndrome (UACS) and gastroesophageal reflux disease (GERD) (2). Eosinophilic airway inflammation, which is observed in 30% to 50% of chronic cough patients, is a common feature of CVA, NAEB and UACS. The response to corticosteroid therapy in these patients is generally very good (3). CVA, an airway disorder characterized by type 2-driven inflammation, is considered the most common cause of chronic cough (4). NAEB, another common cause of chronic cough, is characterized by airway eosinophilic inflammation without airway hyperresponsiveness (5). Previous studies F (6,7) have shown that the Th2 pathway also plays a role in NAEB. However, eosinophilic infiltrates in the airways, blood eosinophilia and chronic cough may be the main characteristics of other conditions, that do not respond to corticosteroid therapy. Type 2-driven inflammation does not appear to be the main mechanistic pathway underlying eosinophilic airway inflammation. Making a clear diagnosis, controll ing eosinophilic airway inflammation and managing cough can be difficult. In this editorial commentary, we describe (I) the possible uncommon causes of chronic cough associated with airway eosinophilia, (II) management of these uncommon causes of chronic cough and (III) mechanistic insights linking eosinophilic airway inflammation and cough. These uncommon conditions include (i) hypereosinophilic syndrome (HES), (ii) IgG4-related disease (IgG4-RD), (iii) Occupational eosinophilic bronchitis.