As pulmonary physicians we continue to struggle with the nature of the disease called COPD (Chronic Obstructive Pulmonary Disease). This disease has been the topic of a number of my articles. Just when I feel we have a good handle on the nature of this disease some new information comes along and muddies the waters.

Recently, pulmonary specialists have been talking about a disease which is unofficially called asthma-COPD overlap syndrome or ACOS. Like most discussions some feel this disease variant exists and others do not. I happen to believe that this condition does exist. ACOS is a condition in which a patient has both COPD, which is associated with non-reversible airway obstruction, and asthma, which has reversible airway obstruction and responds well to medications. This new unofficial disease variant can significantly alter our thoughts about individual therapy. Although COPD and asthma are similar in terms of symptoms there are slight differences in the causes of these disease entities. These differences may be reflected in the way in which we select the combination of medications to treat our patients and the way in which they respond.

Patients with ACOS may have more coughing and wheezing and require more inhaled corticosteroid use owing to the presence of their asthmatic component, whereas patients with pure COPD may need combinations of bronchodilator medications without the steroid component. Patients with ACOS may also have flair ups due to allergies, which is much more common in the asthmatic patient. The conversation about ACOS will continue.