Asthma I: Introduction

Asthma involves chronic airway inflammation that triggers swelling of the airway lining, excess mucus production, and smooth muscle constriction. These three mechanisms narrow the airway lumen and obstruct airflow, making breathing difficult. The underlying inflammation is central to asthma's pathophysiology and contributes to recurring episodes of wheezing and shortness of breath.

Individuals with a family history of asthma, allergic rhinitis, or atopic dermatitis have higher likelihood of developing asthma due to inherited immune and airway traits. Genetic susceptibility makes the airways more reactive to environmental triggers. However, genetics alone does not determine asthma; environmental exposures are also necessary for the disease to develop.

Allergens such as pollen, dust mites, mold spores, pet dander, and cockroach antigens provoke airway inflammation in sensitized individuals. Non-allergic irritants including tobacco smoke, air pollution, chemical fumes, strong odors, and cold air also contribute to airway narrowing. Exercise can similarly trigger symptoms in susceptible individuals.

Respiratory viral infections such as rhinovirus, influenza, and respiratory syncytial virus amplify airway inflammation and increase bronchial reactivity. These infections are among the most significant triggers of asthma exacerbations, particularly in children. Viruses worsen existing inflammation and heighten the airways' sensitivity to other triggers.

Airway hyperresponsiveness is heightened sensitivity of the airways whereby even mild exposures to allergens or irritants provoke exaggerated bronchoconstriction. Chronic airway inflammation causes structural and functional changes in bronchial walls, increasing airway sensitivity. Inflammatory mediators released by immune cells like eosinophils, mast cells, and T lymphocytes drive these alterations.

Asthma presents with recurrent episodes of wheezing, shortness of breath, chest tightness, and coughing. These symptoms typically vary in intensity and may resolve spontaneously or with treatment. The episodic nature reflects the reversible airway obstruction and inflammation characteristic of asthma.

Asthma is characterized by variable airflow obstruction that is partially reversible, either spontaneously or with treatment. In contrast, chronic obstructive pulmonary disease involves largely irreversible airflow obstruction. While both involve airway narrowing, asthma's inflammation-driven changes are reversible, whereas chronic obstructive pulmonary disease causes permanent structural damage to airways and lung tissue.