SELECTED ARTICLES FROM THE RECENT LITERATURE 2007

August 7, 2007

Asthma treatment and prevention – two separate pathways

Summary
Background – Currently many asthma experts share the concept that persistent asthma (PA) is primarily a chronic inflammatory disease of the airways.  As a corollary of this concept the expectation is that inhibition of this inflammation by chronic treatment would prevent progression and irreversible pathology in PA.  But recent findings raise questions about this therapeutic approach.

Findings – This situation was discussed in an editorial by Martinez of the Univ of Arizona.  He described findings in 3 recent clinical trials testing the hypothesis that introduction of inhaled corticosteroid (ICS) treatment at at the beginning of persistent wheezing in young children at high risk for the development of asthma could change the natural course of this disease. In all 3 trials, symptom frequency when off ICS and lung function were not significantly different 2-4 years later in children who were previously treated with ICS or placebo at onset of wheezing.

These findings challenged the concept that the bronchial inflammatory changes responsive to ICS treatment in asthma are also responsible for the chronic changes in airway structure and function now commonly called “airways remodeling” (increased airway smooth muscle mass, sub-epithelial fibrosis, thickened lamina reticularis, mucus gland hyperplasia, increased vascularity).

Another aspect of these studies was that in children with persistent asthma symptoms, most of any declines in lung function occurred by age 6-9 years. In the CAMP study, there was no difference in the lung function growth in those wheezing children treated chronically with ICS or placebo.

Reference
J Allergy Clin Immunol 2007;119:30-3

Editor's Comments
These comments by a prominent investigator of childhood asthma highlights an ongoing debate about the pathogenic role of ICS-responsive bronchial inflammation in PA.  There is general agreement that ICS treatment of PA in young wheezing children leads to decreased asthmatic symptoms, use of rescue mediations, and less frequent acute asthma exacerbations.  But other factors (e.g. – local smooth muscle hyperactivity) may persist despite chronic low – moderate dose ICS treatment.  We are reminded that the pathogenesis of PA is likely quite complex.

 

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