Asthma Severity, Symptoms, Causes, and Diagnosis

Asthma is caused by inflammation within the small airways in the lungs. This inflammation can have multiple negative effects, including bronchoconstriction, increased mucus production, cough, and asthma exacerbations (attacks).

There are several subtypes of asthma. In about half of asthma patients, the lung inflammation is associated with increased numbers of eosinophils, a type of white blood cell. Such asthma is termed "eosinophilic asthma." Increased levels of eosinophils have been associated with increased risk of asthma exacerbations.

Asthma is a complex disease for which different medications are used to treat different components of the disease. Treatment occurs in a stepwise fashion involving the staged use of inhalers and sometimes oral or injected medications, depending on disease severity. Drugs have recently been developed to target the eosinophilic subtype of asthma.