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Thursday, January 15, 2015

Genetics has improved asthma wisdom

Physicians first recognized asthma in the 5th century B.C., and here we are, over 2,500 years later, and they are still trying to figure out this disease.  Compare this with a disease like cystic fibrosis, a disease that wasn't discovered until the 1930s, of which scientists quickly learned was caused by mutations in the CFTR gene.

Unlike cystic fibrosis, it appears that asthma is caused by many genes, each playing a unique role in the development and severity of the disease.  Understanding that there are many genes responsible for asthma may explain why some cases of asthma are more severe than others, why there are so many different things that might cause asthma, why some people have more severe asthma than others, and why asthma medicines don't work for about 10% of asthmatics. 

When the first asthma genes were discovered in the late 1990s, or early 2000s, it was thought that medicine could be invented to block their effect, or shut them off completely.  Although, things rarely work out to be as easy as they initially seem.  As it turns out, there are so many genes responsible for asthma that physicians are still busy discovering them, and still learning what they are responsible for.  

Just to give an example, here are some of the asthma genes that have been discovered to this date.  
  1. Cause people to develop asthma
    • Regulate IgE production
    • Regulate proliferation and maturation of eosinophils and mast cells, and epithelial function
  2. Those that affect a person's response to medicine
    • Cause them to develop a tolerance to bronchodilators like albuterol
    • Cause them to develop a tolerance to systemic and inhaled corticosteroids
These genes can also be broken down into:
  1. Genes that cause asthma by themselves, regardless of exposure to environmental influences:  These might be responsible for early-onset, or childhood onset asthma.  
  2. Genes that are influenced by environmental influences: These might explain why there are so many things that might cause one to develop asthma
This would explain why about 75 percent of asthmatics develop allergies, and therefore develop sensitivities to the various allergens, such as dust mites, cockroaches, molds, fungus, pollen, etc. It may also explain why some asthmatics are overly sensitive to viral and bacterial infections, while others are not.  

It might also explain why some people develop asthma as a response to Asprin or Tylenol, and others do not.  Along the same lines, it might explain why Asprin and Tylenol are asthma triggers in some asthmatics, but do not bother others. 

  1. Elzouki, et al, "Textbook of clinical pediatrics," 2nd edition, 2012, Springer, New York, London, pages 1373-1375

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