Asthma is considered a chronic inflammatory disorder of the tracheobronchial airways and is clinically manifested by recurrent episodes of cough, wheezing, shortness of breath, and sputum production.<sup>14   Expert Panel Report 2: Guidelines for the Diagnosis and Management of Asthma Washington, DC: National Institutes of Health publication (1997).  no. 97-4051.

Cliccare qui per andare alla sezione Riferimenti</sup> Symptoms may range from mild and intermittent in the nearly asymptomatic patient to severe, life-threatening, and sometimes fatal in another. In addition to the concept of inflammation, one key to the understanding of asthma is the recognition of the presence of reversible airway obstruction and bronchial hyperresponsiveness. Acutely, airway obstruction is caused by smooth muscle contraction, increased production of thick, tenacious mucus, shedding of epithelial cells, and airway mucosal edema. Increased sensitivity of the airway, that is, “twitchiness,” to other stimuli heralds the hyperreactivity of the tracheobronchial tree. The treatment of asthma is aimed at reducing and preventing these pathophysiologic events.

Growing evidence suggests that asthma may become partially irreversible over time,<sup>45 Sears M.R. Consequences of long-term inflammation: The natural history of asthma Clin Chest Med 2000 ;  21 : 315-329  [cross-ref]

Cliccare qui per andare alla sezione Riferimenti</sup> and it is postulated that this change occurs owing to smooth muscle hypertrophy caused by chronic inflammatory cytokine effects.<sup>19 Hirst J. Airway smooth muscle as a target in asthma Clin Exp Allergy 2000 ;  30 (suppl 1) : 54-59  [cross-ref]

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