What is Asthma?

DR. SOPHOCLES: Dr. Cox, to begin, exactly what is asthma?
DR. COX: Asthma, as it is defined in 2007, is a common chronic disorder of the airways that is complex and characterized by variable and recurrent symptoms such as wheezing, SOB, or cough. These are symptoms due to airflow obstruction that can come from hyper-responsiveness of the bronchial tubes to various stimuli, and an underlying inflammation probably plays a big role in causing this hyper-responsiveness. The interactions of these features in asthma determine the clinical manifestations and severity of asthma. What we know now is asthma is not one single disease entity.

There are various types of asthma due to having various phenotypes and these different types of asthma may respond differently to medications. So there is growing recognition there is a genetic component to asthma as well as an influence of the environment. Recently, the National Heart Lung and Blood Institute issued their third update on asthma management and diagnosis. The basis for this presentation is to summarize the highlights of this very comprehensive report.

DR. SOPHOCLES: What does the chronic inflammation associated with asthma do to the lungs and does it cause permanent damage?
DR. COX: For years, we’ve recognized that inflammation is a key feature of asthma, but we now recognize that there seem to be different types of asthmatics and they may not all respond to the same type of medication regimen. In some patients, certain medications may actually make their asthma worse. We’ll talk a little bit about Beta-Agonists and some of the controversies around this. We recognize that airway inflammation contributes to the hyper-responsiveness in asthma. Various different phenotypic patterns of asthma exist in the presence of underlying airway inflammation—which is variable and has distinct but overlapping patterns that reflect different aspects of the disease, such as making one intermittent versus persistent asthmatic. But airway inflammation is the key feature.

The inflammatory cell infiltrate in asthma includes a number of different cells: neutrophils, eosinophils, lymphocytes, mast cell, and as a result of this complex concert of cellular infiltration, there is damage to the epithelium of the lungs. In biopsies of asthmatics that have had long-standing asthma, you can see a number of different pathological processes that we believe now contribute to a concept that we have referred to in the past as airway remodeling.

What happens is there is dysfunction of the cilia, the fine hair cells in the mucous membranes. There is sloughing off of the epithelium. There is increased mucin production. There is hypertrophy of the smooth muscle of the airway, increased blood vessel or angiogenesis growth, and a number of inflammatory cells that you can find in these biopsy specimens.