Asthma

• A common disorder in which chronic inflammation of the bronchial tubes (bronchi) makes them swell, narrowing the airways.
  • Asthma involves only the bronchial tubes and does not affect the air sacs (alveoli) or the lung tissue (the parenchyma of the lung) itself.
• Airway narrowing in asthma is due to three major processes acting on the bronchi:
  • inflammation
  • spasm (bronchospasm)
  • hyperreactivity (over-reaction of the bronchi to factors that can precipitate asthma)

Cause

The incidence of asthma has risen dramatically in the past 20 years, a period far too short to reflect any significant changes in the gene pool. This supports the important role that environmental influences (allergy, infection, lifestyle, and diet) have on the development of asthma.

• Several studies conclude that heredity increases ones chances of developing asthma, particularly if allergies or other allergic conditions are present.
• So, what are the chances that a child will develop asthma?
  • 6.5% of families in which neither parent has asthma have a child with asthma.
  • 28% of families in which one parent has asthma have a child with asthma.
  • 63% of families in which both parents have asthma have at least one child with asthma
• A hunt lasting a decade and spanning two continents led in 2004 to the finding of two asthma genes on chromosome 7p.
  • A candidate gene was found encoding a G protein-coupled receptor named GPRA (G protein-coupled receptor for asthma susceptibility).
  • GPRA appears involved in the susceptibility to allergy and asthma.
• Inheriting genes for asthma does not necessarily mean that a person will definitely develop asthma
• The susceptibility genes together with the asthma-promoting factors in your environment, and your lifestyle can all conspire to put you at risk for developing asthma
• Many environmental factors are known to precipitate attacks of asthma. These factors are all either allergens or irritants.

Signs and symptoms

• shortness of breath
• chest tightness
• cough
• wheezing
• diagnosis is based on these features (without wheezing, it is not asthma) and is confirmed with breathing tests
  • Chest X-rays are usually normal in people with asthma.

Treatment

• bronchial narrowing characteristic of asthma can be partially or completely prevented or reversed with proper treatment, such as bronchodilators like salbutamol (beta receptor agonist)
• corticosteroids can be prescribed to reduce inflammation, but have many potential side effects
• avoiding precipitating factors is important in managing asthma