Bronchiectasis Explained: Pathophysiology, Prevalence, and Evolving Models

Welcome back to another AJMC Insights series. In "Bronchiectasis Explained: Pathophysiology, Prevalence, and Evolving Models," Colin Swenson, MD opens the series by walking through how the field's understanding of bronchiectasis pathophysiology has evolved and why its prevalence is rising faster than many appreciate.

Dr. Swenson begins by acknowledging that much about bronchiectasis pathophysiology, especially non-CF bronchiectasis, remains poorly understood. He defines bronchiectasis as permanent, irreversible widening of the airways in adults. That widening is driven primarily by chronic infection and inflammation, he explains, with neutrophils responsible for roughly 80% of the inflammatory activity. Neutrophil recruitment into the airway lumen sustains a chronic inflammatory response that gradually remodels and enlarges the airways over time. Dr. Swenson identifies mucus plugging as a major driver of disease, noting that it compromises oxygen delivery to the airway lining and accelerates further remodeling. He describes this dynamic as the vicious vortex model, in which separate domains of inflammation, infection, and structural damage continuously interact rather than progressing in a straight line.

Reflecting on how his understanding has changed since fellowship, Dr. Swenson recalls training under Cole's vicious cycle model, an earlier framework that treated infection, inflammation, and airway damage as a linear, repeating sequence. Clinicians now recognize that these domains influence one another dynamically rather than following that fixed order, he says. Turning to epidemiology, Dr. Swenson reports that bronchiectasis prevalence is rising worldwide. In the United States, an estimated 500,000 to 700,000 adults carry the diagnosis, though he believes the true figure is considerably higher, particularly among Medicare beneficiaries 65 and older. Large studies tracking prevalence over a decade show annual increases of roughly 5% to 8%, he notes. Dr. Swenson emphasizes that these numbers challenge the perception of bronchiectasis as a rare disease, arguing that its growing footprint demands greater clinical attention across specialties.

The next episode in this series, "How Bronchiectasis Feels: Symptoms and Daily Patient Burden," turns to how these same pathophysiological changes translate into the symptoms patients actually feel day to day.