Eos is the medical shorthand abbreviation for a white blood cell called an eosinophil.  These cells were discovered in the human blood stream in the late 1800’s and get their name from the color they stain when we look at a blood sample under the microscope.

The importance of eos is currently the subject of new and increased interest in lung disease.  We have known for some time that eos are important in patients with asthma.  Eos contain a variety of chemical “packets”, which are unleashed as part of the inflammation associated with asthma.  Recently, the role eos may play in COPD has been under some research scrutiny. 

It appears that patients with COPD may be divided into two groups: one with increase eos in their blood and ones without.  The difference in these two groups may be significant, e.g. COPD patient with higher eos in their blood respond quicker to therapy and spend less time in the hospital when they have an exacerbation.  However, they also relapse quicker following discharge if corticosteroid therapy is abruptly discontinued.

Are COPD patients really patients with some form of asthma and need to be considered for special therapies that we currently reserve for asthma patients? We have medications now available which can potentially control the population of eos in the blood stream, but these are currently only approved for use in asthma patients. There is some early data that suggests these therapies, along with conventional treatment, may prove beneficial.  Stay tuned.