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Table 1 Asthma Definitions

From: Severe asthma and the omalizumab option

Manifestation Definition
Asthma Inflammatory disease of the airways characterized by:
     • Infiltration by eosinophils, lymphocytes and neutrophils
     • Mast cell activation
     • Epithelial loss
  Associated reversible airway obstruction, recurrent symptoms and bronchial hyper-responsiveness
  Gene-by-environment interactions are important
Inflammation Plays central role in asthma pathophysiology
  Mediated by T cells, lymphocytes, mast cells, eosinophils and epithelium. Other resident cells such as fibroblasts and smooth muscle play a role
Airway remodeling As inflammation proceeds, other changes evolve leading to reparative or remodeling changes and include:
     • Sub-basement membrane thickening
     • Subepithelial fibrosis
     • Smooth muscle hypertrophy
     • Angiogenesis
  Mucus gland hyperplasia and hypersecretion
Bronchoconstriction Airway narrowing resulting in wheezing
  Probably acutely due to release of mast cell mediators such as histamine, leukotrienes, and tryptase
  Obstruction could be mediated by multiple factors:
     • Smooth muscle contraction
     • Airway edema
     • Airway remodeling and fibrosis
Bronchial Hyperresponsiveness Exaggerated bronchoconstrictive response to a wide variety of stimuli; best measured clinically by methacholine challenge testing; mediated by inflammation, remodeling and other airway changes that occur in asthma