Article Sections

Introduction

Asthma is a chronic disorder of the airways characterized by reversible airflow obstruction with bronchial hyperresponsiveness and underlying inflammation.  This article highlights the pathophysiology and clinical manifestations of asthma; management is detailed in a separate article.

Pathophysiology

The cellular basis of asthma is leukocyte-induced bronchoconstriction ( Figure 1).  A combination of host susceptibility (eg, atopic genetic background) and environmental exposure (eg, dust mites, tree pollen) are involved in leukocyte priming, specifically upregulating the Th2 axis (ie, IL-5 primes eosinophils, IL-4 and IL-13 prime IgE production).

These primed (sensitized) leukocytes are easily activated ( Table 1) under certain circumstances (eg, reexposure to allergen; upper respiratory infection; cold, dry air).  When activated, they release preformed inflammatory mediators (eg, histamine, prostaglandins, leukotrienes) that cause episodes of bronchoconstriction, airway edema, and mucus hypersecretion.  These events are known as asthma exacerbations.

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Figures

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Tables

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