This information is taken from the revised 2007 GINA Report, Global Strategy for Asthma Management and Prevention, available on the Global Initiative for Asthma (GINA) website. Please refer to the full guideline document1 for more detailed information.
Asthma is a disorder defined by its clinical, physiological, and pathological characteristics. The predominant feature of the clinical history is episodic shortness of breath, particularly at night, often accompanied by cough.
Wheezing appreciated on auscultation of the chest is the most common physical finding.
The main physiological feature of asthma is episodic airway obstruction characterized by expiratory airflow limitation. The dominant pathological feature is airway inflammation, sometimes associated with airway structural changes.
Asthma has significant genetic and environmental components, but since its pathogenesis is not clear, much of its definition is descriptive. Based on the functional consequences of airway inflammation, an operational description of asthma is:
Asthma is a chronic inflammatory disorder of the airways in which many cells and cellular elements play a role. The chronic inflammation is associated with airway hyperresponsiveness that leads to recurrent episodes of wheezing, breathlessness, chest tightness, and coughing, particularly at night or in the early morning. These episodes are usually associated with widespread, but variable, airflow obstruction within the lung that is often reversible either spontaneously or with treatment.
Because there is no clear definition of the asthma phenotype, researchers studying the development of this complex disease turn to characteristics that can be measured objectively, such as atopy (manifested as the presence of positive skin-prick tests or the clinical response to common environmental allergens), airway hyperresponsiveness (the tendency of airways to narrow excessively in response to triggers that have little or no effect in normal individuals), and other measures of allergic sensitization. Although the association between asthma and atopy is well established, the precise links between these two conditions have not been clearly and comprehensively defined.
There is now good evidence that the clinical manifestations of asthma—symptoms, sleep disturbances, limitations of daily activity, impairment of lung function, and use of rescue medications—can be controlled with appropriate treatment. When asthma is controlled, there should be no more than occasional recurrence of symptoms and severe exacerbations should be rare.1
References:
1. Revised 2007 GINA Report, Global Strategy for Asthma Management and Prevention