RT Journal Article SR Electronic T1 Pathological features and inhaled corticosteroid response of eosinophilic and non-eosinophilic asthma JF Thorax JO Thorax FD BMJ Publishing Group Ltd and British Thoracic Society SP 1043 OP 1049 DO 10.1136/thx.2006.073429 VO 62 IS 12 A1 Mike Berry A1 Angela Morgan A1 Dominick E Shaw A1 Deborah Parker A1 Ruth Green A1 Christopher Brightling A1 Peter Bradding A1 Andrew J Wardlaw A1 Ian D Pavord YR 2007 UL http://thorax.bmj.com/content/62/12/1043.abstract AB Background: Non-eosinophilic asthma is a potentially important clinicopathological phenotype since there is evidence that it responds poorly to inhaled corticosteroid therapy. However, little is known about the underlying airway immunopathology and there are no data from placebo-controlled studies examining the effect of inhaled corticosteroids.Methods: Airway immunopathology was investigated using induced sputum, bronchial biopsies, bronchial wash and bronchoalveolar lavage in 12 patients with symptomatic eosinophilic asthma, 11 patients with non-eosinophilic asthma and 10 healthy controls. The patients with non-eosinophilic asthma and 6 different patients with eosinophilic asthma entered a randomised, double-blind, placebo-controlled crossover study in which the effects of inhaled mometasone 400 μg once daily for 8 weeks on airway responsiveness and asthma quality of life were investigated.Results: Patients with non-eosinophilic asthma had absence of eosinophils in the mucosa (median 4.4 cells/mm2 vs 23 cells/mm2 in eosinophilic asthma and 0 cells/mm2 in normal controls; p = 0.03) and normal subepithelial layer thickness (5.8 μm vs 10.3 μm in eosinophilic asthma and 5.1 μm in controls, p = 0.002). Non-eosinophilic and eosinophilic asthma groups had increased mast cell numbers in the airway smooth muscle compared with normal controls (9 vs 8 vs 0 cells/mm2, p = 0.016). Compared with placebo, 8 weeks of treatment with inhaled mometasone led to less improvement in methacholine PC20 (0.5 vs 5.5 doubling concentrations, 95% CI of difference 1.1 to 9.1; p = 0.018) and asthma quality of life (0.2 vs 1.0 points, 95% CI of difference 0.27 to 1.43; p = 0.008).Conclusions: Non-eosinophilic asthma represents a pathologically distinct disease phenotype which is characterised by the absence of airway eosinophilia, normal subepithelial layer thickness and a poor short-term response to treatment with inhaled corticosteroids.