Bronchial asthma is an inflammatory process that affects the small and medium-sized airways. Common physiologic characteristics include the following:
Excessive mucus production and mucosal edema
Bronchial smooth muscle contraction and hyper-reactivity
Eosinophilia and increased serum immunoglobulin E (IgE)
Positive food/inhalant allergy test
Deposition of matrix leading to remodeling of the airway
It used to be thought that asthma did not lead to permanent airway changes (such as emphysema), but more recent research demonstrates prolonged inflammation can cause permanent damage.
Most patients experience a set of clinical symptoms which result in the sensation of difficulty breathing. The clinical manifestations of asthma are:
Recurrent attacks of dyspnea (shortness of breath)
Cough
Expectoration
Prolonged expiratory phase with wheezing
The symptoms can be present in any combination, or in isolation. Some patients are unaware that they have asthma if their clinical manifestation is isolated to coughing alone. This is particularly true for exercise-induced asthma or cold-induced asthma.