Purpose of review: The lack of a universally accepted definition of chronic severe asthma and the continuous changes in the classification of the severity of stable chronic obstructive pulmonary disease in the last 10 years make it difficult to compare the many studies available. The aim of the review is to compare studies on chronic severe asthma that have a control group of patients with mild to moderate persistent asthma and studies on stable chronic obstructive pulmonary disease that have an age-matched control group of smokers with normal lung function (with or without chronic bronchitis).
Recent findings: Our review of the recent literature in this field seems to indicate that chronic airway inflammation in chronic severe asthma is characterized in most cases, both in central and peripheral airways, by the same pathological features of mild-moderate persistent asthma with an increased number of activated T lymphocytes, particularly CD4 Th2 cells, and sometimes eosinophils and mast cells. The most notable difference of chronic severe asthma compared with mild to moderate disease is the increased number of neutrophils. Chronic airway inflammation in stable chronic obstructive pulmonary disease is characterized, both in central and peripheral airways, by an increased number of T lymphocytes, particularly CD8+, macrophages and neutrophils. Macrophage and neutrophil counts increase with the progression of the severity of the disease.
Summary: These differences in chronic airway inflammation support the consensus that asthma and chronic obstructive pulmonary disease are different diseases along all their stages of severity.