Asthma

Asthma is a chronic inflammatory disease that obstructs the airways, but it is important (and often difficult) to distinguish it from COPD. In some patients (about 15% in most studies), the conditions occur simultaneously. However, the natural history of the COPD and asthma are distinctly different, with different etiologies and different treatments.

Inflammatory cells (particularly mast cells, T lymphocytes, and eosinophils), mediators, and airway tissue and cells are involved in asthma. According to the Global Initiative for Asthma, a project conducted in collaboration with the National Heart, Lung, and Blood Institute, National Institutes of Health, and the World Health Organization, the interaction of these cells result in acute bronchoconstriction, swelling of the airway wall, increased mucus secretion, airway remodeling, and inflamma­tion.  According to the Global Initiative for Asthma, “the morphologic changes that occur in asthma include bronchial infiltration by inflamma­tory cells (mast cells, T lymphocytes, and eosinophils are key effector cells in the inflammatory response), mucus plugging of the airways, interstitial edema, and microvascular leakage. Destruction of bronchial epithelium and thickening of the sub-basement membrane are characteristic. There may also be hypertrophy and hyperplasia of airway smooth muscles, increase in goblet cell number, and enlargement of submucus glands.”

Because of the inflammation, the airways are chronically sensitive or hyperresponsive. When the airways are irritated, airflow is limited and an exacerbation (or asthma attack) may occur. These attacks, which may be mild, moderate, or severe, are characterized by coughing, wheezing, chest tightness, and difficult breathing.

Unlike COPD, allergy is strongly associated with asthma. Risk factors for the development of asthma include common allergens (eg, dust mites, pollen, molds) and chemical or airborne irritants. Viral respiratory infections, size at birth, and diet may also contribute to the development of asthma. As we have already learned, the CD4+ T cells recognize foreign antigens, ultimately leading to the immune response. This is in contrast to COPD, in which CD8+ T cells—that are not responsible for recognizing foreign antigens - play a more prominent role. The introduction of the antigen into the respiratory system produces IgE antibody, which attaches to mast cells. When the antigen is reintroduced into the system, it binds to the mast cells and creates an IgE-mediated, antigen-antibody response.

Another important feature of asthma is an increased responsiveness of the airways to outside stimuli such as the inhalation of cold air and exercise, as well as the pharma­cologic stimulation of inhaled aerosols of bronchoconstrictor substances.

Unlike chronic bronchitis and emphysema, asthma affects people of all ages, including children. Half of all asthma sufferers are diagnosed before they are 10 years old. Another third are diagnosed before age 40.

In summary Asthma is;

• a chronic inflammatory disease that obstructs airways, it may occur simultaneously with COPD
• inflammatory cells, mediators, and airway tissue and cells are all involved, and airways are chronically sensitive
• attacks are characterized by coughing, wheezing, chest tightness, difficulty breathing unlike COPD, asthma is strongly associated with allergies.