Eosinophilic bronchitis – Chronic cough with a treatable trait

Abstract

Eosinophilia in sputum is an important finding in patients with chronic cough, as it identifies a treatable trait with available therapy that is well tolerated and can be effective. While most patients have airway hyperresponsiveness or airway obstruction which define asthma, an important number of cases lack these features of bronchoconstriction but sputum induction still demonstrates excess eosinophilia, indicating eosinophilic bronchitis without asthma. Unfortunately, this test is largely limited to research centers and speciality cough clinics, but associated measures of allergic airway inflammation can be used to support the diagnosis. While the mechanisms that initiate and drive non-asthmatic eosinophilic bronchitis (NAEB) are not well understood, there is emerging evidence that eosinophils and inflammatory mediators are important contributors of nerve sensitivity, a hallmark of chronic cough. Inhaled steroids form the major treatment used in non-asthmatic eosinophilic bronchitis (NAEB). Novel targeted therapies for asthma known as biologics are likely to be tried in the common and debilitating condition of chronic cough, while their efficacy in NAEB is yet to be seen.