Why is asthma classified as a disease?

Why Asthma is Classified as a Disease

Asthma is classified as a disease because it represents a chronic pathological disorder of the airways characterized by persistent inflammation, structural airway remodeling, and bronchial hyperresponsiveness that causes significant morbidity, mortality, and impaired quality of life through recurrent episodes of airflow obstruction. 1, 2

Core Pathological Features That Define Asthma as a Disease

Chronic Inflammatory Process

• Asthma fundamentally involves chronic inflammation of the airways that persists even when patients are asymptomatic, distinguishing it from normal physiological responses. 2, 3
• The inflammatory process involves multiple cellular players working abnormally, including mast cells, eosinophils, T lymphocytes, macrophages, and epithelial cells, creating a pathological state rather than a temporary condition. 2
• This inflammation drives three interconnected pathophysiologic processes: bronchoconstriction, bronchial hyperresponsiveness, and progressive airway remodeling. 2, 3

Structural Airway Damage (Remodeling)

• Persistent inflammation leads to permanent structural changes in airway architecture, including sub-basement membrane fibrosis, smooth muscle hypertrophy, epithelial cell injury and shedding, angiogenesis, and mucus gland hyperplasia. 2
• These structural changes explain why airflow limitation may become incompletely reversible in some patients despite aggressive treatment, representing true pathological tissue damage. 2
• The repeated cycles of inflammation with injury to pulmonary tissues followed by repair produce long-term structural changes that distinguish asthma from transient respiratory symptoms. 4

Abnormal Physiological Function

• Asthma causes bronchial hyperresponsiveness, where airways develop an exaggerated bronchoconstrictor response to stimuli that would not affect normal airways. 2
• This represents a fundamental abnormality in airway function, with wide variations in airflow limitation over short periods of time that are not seen in healthy individuals. 5
• The variable and reversible airflow obstruction is often reversible either spontaneously or with treatment, distinguishing it from fixed obstructive diseases but still representing pathological dysfunction. 3, 1

Disease Classification Criteria Met by Asthma

Measurable Morbidity and Mortality

• Underdiagnosis and inappropriate therapy contribute substantially to asthma morbidity and mortality, establishing it as a condition with serious health consequences. 1
• Asthma is responsible for more than €20 billion per year in healthcare expenditures, driven primarily by asthma exacerbations requiring emergency department visits, hospitalizations, school absences, and loss of parental workdays. 1
• Real-life data shows that four out of 1000 children with asthma experience a severe exacerbation per follow-up year, and 25% will experience another within 1 year, demonstrating significant disease burden. 1

Genetic and Environmental Disease Basis

• There is a strong genetic component to asthma, with 80% of children with two asthmatic parents developing asthma, indicating an inherited disease susceptibility. 2
• Gene-environment interactions are critical, with environmental exposures during immune system development being essential for disease manifestation. 2
• In utero exposures such as maternal smoking increase childhood asthma risk in a dose-dependent pattern, demonstrating clear disease causation pathways. 2

Distinct Clinical Syndrome

• The International Consensus Report describes asthma as "a chronic inflammatory disorder of the airways" with inflammatory symptoms associated with widespread but variable airflow obstruction and increased airway response to various stimuli. 1
• Asthma produces characteristic recurrent episodes of coughing, wheezing, breathlessness, and chest tightness that are variable, intermittent, worse at night, and provoked by specific triggers. 1, 3
• The disease can be objectively confirmed through spirometry showing reversible airway obstruction, distinguishing it from normal respiratory variation. 3, 6

Common Pitfalls in Understanding Asthma as a Disease

Avoiding Minimizing Labels

• Avoid underdiagnosing asthma by using labels such as "wheezy bronchitis," "recurrent pneumonia," or "reactive airway disease," which can miss the opportunity to treat appropriately and fail to recognize the underlying chronic disease process. 3
• The absence of an agreed single definition has been problematic, but this reflects disease heterogeneity rather than absence of true pathology. 1

Recognition of Disease Even Without Symptoms

• Patients with asthma can have normal lung function between exacerbations, but the underlying inflammatory disease process persists. 1
• Inflammation can be present even in patients with mild asthma when they have few symptoms, emphasizing that asthma is a chronic disease state rather than episodic symptoms alone. 2

Disease Heterogeneity Does Not Negate Disease Status

• Different asthma phenotypes exist with varying patterns of inflammation, cellular mediators, and therapeutic responses, but all represent pathological disease states. 2
• The shift from phenotype evaluation towards endotype analysis has allowed better understanding of clinical differences, with T2-high and T2-low endotypes representing distinct disease mechanisms. 1