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SELECTED ARTICLES FROM THE RECENT LITERATURE 2008
November 5, 2007
The relationship between asthma and eosinophilic bronchitis
Summary
Eosinophilic bronchitis (EB) presents as a chronic cough. It shares bronchial eosinophilia and peripheral blood eosinophilia with asthma. It accounts for perhaps 10% of referrals to specialist cough clinics. The differences between eosinophilic bronchitis and asthma are:
- In asthma, there is infiltration of the smooth muscle with mast cells. This does not occur in eosinophilic bronchitis.
- Bronchospasm is not a feature of eosinophilic bronchitis. However, some patients with this disorder, over time, develop fixed airway obstruction.
- Eosinophilic bronchitis patients do not have airway hyperreactivity.
- In asthma, eosinophils and mast cells in the bronchial submucosa and eosinophils in the peripheral blood over-express IL-13 - this is not present in eosinophilic bronchitis.
The authors of this study wanted to determine whether vascular endothelial growth factor (VEGF), which is known to be overexpressed in the asthmatic airway, is also increased in eosinophilic bronchitis, and to examine the association of vascular remodeling with airway hyperresponsiveness in asthmatics.
They found that sputum VEGF concentration was increased in both asthmatics and patients with eosinophilic bronchitis. Moreover they found that although vascular remodeling affected post bronchodilator FEV1 in asthma, it was not associated with airway hyperreactivity. Thus, they postulated that remodeling and airway hyperreactivity may be independent and that the remodeling process may protect against airway hyperreactivity.
Editor's Comments
Angiogenesis has long been known to be a feature of the pathology of asthma and has been classified as one of the changes occurring with the remodeling process. It has been thought to contribute to airway hyperreactivity. The authors used eosinophilic bronchitis, a condition without airway hyperreactivity, but with eosinophilia and elevated VEGF to study the role of neovascularity in producing both chronic obstructive disease and airway hyperreactivity. They found that it does affect post bronchodilator FEV1 but played no role in the production of airway hyperreactivity. Both patients with eosinophilic bronchitis and asthma demonstrated elevations of VEGF.
Reference
Siddiqui S, et al. Vascular remodeling as a feature of asthma and non-asthmatic eosinophilic bronchitis. J Allergy Clin Immunol 2007; 120:813-819.
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