Pascal Chanez

Limited Short-term Steroid Responsiveness Is Associated With Thickening of Bronchial Basement Membrane in Severe Asthma

BACKGROUND The clinical manifestations of bronchial remodeling in asthma and the potential impact of this process on lung function remain unclear. We aimed to determine whether the presence of pathologic features of airway remodeling in patients with asthma was associated with steroid responsiveness in the short term. METHODS Sixty-three consecutive patients with severe asthma with chronic airflow impairment (post-bronchodilator FEV(1) < 80% predicted values) were recruited, clinically characterized, and had an initial bronchoscopy where endobronchial biopsy and BAL were performed. BAL cellular content was reported and reticular basement membrane (RBM) thickness was measured by validated repeated measures. Patients were then treated with 1 mg/kg/d of methyl prednisone, directly administered IV, for 10 days. A threshold of 15% FEV(1) improvement was used to discriminate responsive (group 1) and refractory patients (group 2). RESULTS Thirty-eight patients had a steroid responsiveness > 15% (group 1) and a thinner RBM at the biopsy level (5.78 ± 2.0 μm vs 7.60 ± 2.2 μm; P = .001) compared with nonsteroid responsive group 2 patients as defined. The best predictors for being unresponsive were no long-term treatment with oral steroids and increased RBM thickness. The associated receiver operating characteristic curve indicated that RBM thickness could predict steroid responsiveness below 15% with an area under the curve of 0.747 (P = .0002) at a threshold of 7 μm. CONCLUSIONS Features of airway remodeling are associated with limited short-term steroid responsiveness in severe asthma.

L'asthme: une maladie de tout l'arbre aerien.

Inflammation and remodelling are constant features of asthma. They are present throughout the whole bronchial tree, even in the small airways (less than 2 mm). The inflammatory cell infiltrate and structural changes are, in most cases, identical. However, in severe asthma, nocturnal asthma and fatal asthma, the cellular infiltrate in the distal airways is more intense and the number of activated cells is increased. In fatal asthma there are major alterations in the distal airways involving the smooth muscle and the bronchial epithelium, and mucus hypersecretion leading to distal airway plugging. Thus the histopathological changes in the distal airways contribute to the most severe stages of asthma and should be targeted by treatment. Currently the non-invasive tools that reflect inflammation are unable to assess these changes in the distal airways.