Asthma‐chronic obstructive pulmonary disease overlap: A clinical entity?

Abstract

Asthma and COPD are easily recognizable clinical entities in their characteristic presentations. Asthma is an early-onset disorder characterized by Type 2, eosinophil-predominant, inflammation of the airways and is associated with atopy. COPD presents in middle age and is characterized by neutrophilic inflammation of the airways and is associated with cigarette smoking or biomass fuel exposure. Between exacerbations, asthma typically has normal lung function whereas COPD has incompletely reversible lung function. Approximately one in five patients with either of these disorders will show some features of both COPD and Asthma. This overlap is far more common than can be accounted for by chance concurrence of two common diseases. There are likely genetic and environmental susceptibilities to both disorders, but there is no single pathobiological mechanism that identifies all such overlap patients. Most likely there are numerous predispositions that lead to Asthma-COPD overlap that may be grounded in early childhood or even pre-natal events. Thus, Asthma-COPD overlap is best considered a family of diseases with overlapping clinical manifestations. The future elucidation of these different pathways to Asthma-COPD overlap, in conjunction with highly targeted therapies will aid clinicians in treating these patients.