The role of the microbiome in asthma inception and phenotype
Asthma that occurs de novo in adults, without any evidence of airway hyperreactivity or narrowing in childhood, is increasingly recognized. Indeed, asthma in the elderly has been recognized for decades, and the prevalence of asthma in this population also is increasing. The mechanisms proposed by which people develop asthma or are pre-disposed to its development are numerous. From a century ago when the origin of asthma was considered to be allergic in nature, we now understand increasingly that asthma is a rich interplay of genetics, inflammation, and environmental exposures. Of the latter, allergens, pollutants, and viral infection long have been identified, but increasingly, both the microbiome of the lungs and that of the gastrointestinal system ("gut microbiome") are increasingly understood to have some role, though the mechanisms by which each might do so, and the interplay between them, and of each with other environmental and inflammatory cues, are yet to be understood.
