Asthma – Heterogeneity and The Key Points of Asthma
The Heterogeneity of Asthma
Asthma is one of the most common, if not the most common, chronic disease in children. It is estimated that over 5% of the global population has asthma, which translates to a staggering 350 million people worldwide. It is more common in developed countries, where incidence rates can run as high as 20%. The incidence has also been increasing, first in developed countries, and now in developing nations. Mortality rates of asthma show no significant improvement despite the development of new drugs and strategies to treat asthma. Yet for a disease that affects so many people, there is no single diagnostic test available, and the ability to make a diagnosis depends solely on the clinical skills of the modern day physician. It is a huge challenge.
The early descriptions noted above describe an “obstruction,” and even as recently as 30 years ago, our belief was that asthma was a condition primarily of bronchoconstriction. The clinical results of these inflammatory changes are cough, wheezing, respiratory distress, inadequate oxygenation of blood and clearance of carbon dioxide, respiratory acidosis and potentially, death. If the changes are chronic, then there can be permanent damage to the structure of the airway epithelium, a process loosely known as “airway remodeling,” leading to the development of an irreversible process more closely resembling chronic obstructive pulmonary disease or emphysema.
A current definition of asthma, based on what we expect to happen as a result of these cellular events that ultimately lead to the symptoms of asthma, may be as follows:
Asthma is a recurrent respiratory illness of varying severity resulting from inflammation of the airways, which can cause bronchoconstriction and mucous production, leading to cough, wheezing and dyspnea, that if untreated, can be potentially fatal.
- Asthma is a heterogeneous disease, presenting in many forms.
- There is no pathognomonic test for asthma, and the diagnosis is based on clinical presentation.
- Ancillary tests and procedures can only assist in making the diagnosis, and should be taken in context with the clinical history and physical.
- Radiographs are particularly not helpful in defining asthma, due to the lack of specificity.
- The development of asthma is dependent on the interaction between multiple genetic and environmental factors.
- The hallmark of asthma is airway inflammation.
- The concept of airway remodeling in asthma is poorly defined and still incompletely understood.
- Asthma in children can be triggered by allergies, viral upper respiratory infections and exercise.
- The onset of asthma can occur at any age, but it more frequently begins in childhood.
- Asthma in the elderly presents a unique problem as other diseases of the lung and other organs can exist concurrently.
(Source: Bronchial Asthma – A Guide for Practical Understanding and Treatmen, M. Eric Gershwin MD, MACP & Timothy E. Albertson MD, MPH, PhD)