Asthma

Asthma is a chronic inflammatory disorder of the airways characterized by variable airflow obstruction, bronchial hyperresponsiveness, and respiratory symptoms such as wheezing, cough, chest tightness, and shortness of breath.

Definition

Epidemiology

Affects approximately 1–18% of the global population depending on region
Commonly begins in childhood, though adult-onset asthma also occurs
Prevalence higher in males during childhood and higher in females in adulthood
Significant cause of morbidity, healthcare utilization, and reduced quality of life
Genetic predisposition and environmental exposures influence incidence

Etiology

Genetic susceptibility: family history of asthma or atopy
Allergens: dust mites, pollen, animal dander, mold
Environmental factors: air pollution, tobacco smoke, occupational exposures
Respiratory infections, especially in early childhood
Obesity and dietary factors may contribute
Exercise or cold air can trigger bronchospasm
Stress and psychosocial factors can exacerbate symptoms

Pathophysiology

Chronic airway inflammation with eosinophils, mast cells, and T-helper 2 lymphocytes
Bronchial hyperresponsiveness to triggers
Airway remodeling over time leading to thickened airway walls and smooth muscle hypertrophy
Excess mucus production and airway edema
Intermittent airflow obstruction causing wheezing and dyspnea
Immunologic hypersensitivity reactions contributing to inflammation
Interaction of genetic and environmental factors influencing disease severity