Nonasthmatic Eosinophilic Bronchitis: A Systematic Review of Current Treatment Options

Nonasthmatic eosinophilic bronchitis is characterized by persistent dry or barely productive cough and bronchial eosinophilia without airway obstruction or bronchial hyperreactivity. It is primarily a chronic disease, in which some patients have clinical and pathophysiological relapses, while others progress to asthma or chronic obstructive pulmonary disease. It accounts for 5% to 30% of cases referred for chronic cough. Exposure to common inhalants and occupational sensitizers has been proposed as a possible cause of the disease, although the etiology and underlying mechanisms are uncertain. Some features are similar to those of asthma, such as airway eosinophilia, inflammatory mediator levels, and airway remodeling. Differences in airway pathophysiology, such as the location of airway inflammation and levels of IL-13 and PGE-2, have been reported. Sputum cell count is the gold standard test for diagnosis, and other biomarkers, such as exhaled nitric oxide, could support the diagnosis. A systematic review of treatments for the disease shows that while inhaled corticosteroids are the primary option, the appropriate dose, the type of corticosteroid, and the duration of treatment remain unknown. Treatment duration is inversely correlated with the relapse rate. Increased doses of inhaled corticosteroids, oral corticosteroids, and leukotriene receptor antagonists are recommended in persistent disease. Anti-IL-5 biologics could be promising in this disease. Studies that investigate biomarkers for diagnosis and prognosis are necessary, as are randomized controlled studies for second-line treatments.