Asthma COPD overlap syndrome: Nothing new under the sun

Synopsis

The debate about whether asthma and chronic obstructive pulmonary disease (COPD) are distinct clinical syndromes is not new, but there has been a heightened interest in recent years in understanding the group of individuals with obstructive lung disease who appear to have elements of both asthma and COPD. These patients are of interest because of recent studies which have demonstrated increased risk for respiratory events and exacerbations in this group. We describe the clinical characteristics of this subtype of disease and suggest 4 working definitions of individuals who would fall into the asthma/COPD overlap category. These definitions shed light on the clinical and inflammatory characteristics surrounding the group with overlap syndrome in order to better understand the biologic mechanisms for their worsened outcomes. Understanding the mechanisms underlying these subtypes will hopefully lead into a better understanding of therapeutic strategies that can target specific pathobiologic pathways.