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Tuesday, November 10, 2015

Links between asthma and genetics

The following was originally published at on March 25, 2015.

The Link Between Asthma and Genetics

The discovery of asthma genes has lead to better wisdom about asthma. The hope is that this will some day lead to better treatment, and ideally a cure. In the meantime, here is what is now known about the link between asthma and genetics.

1. A brief history. Around 400 B.C. Hippocrates suspected asthma was hereditary. Since then, asthma has been treated as a single disease, with the treatment being the same for all asthmatics. Since the 1980s most cases of asthma are treated with corticosteroids. While this strategy usually works, it fails to work for some. Genetic research may help explain this.

2. What is genetics? It’s the science of how genes control the characteristics of a person. Think of it this way. The human body is composed of 37.2 trillion cells. Every cell has a nucleus, inside of which is a DNA molecule consisting of genes. Each gene contains a recipe for creating a protein, and each protein carries out some bodily function. Researchers have been studying genetics to determine its role in asthma for many years now.

3. Asthma is hereditary. Genetic researchers have learned that most genes are the same in all people, although about one percent are unique, making every person unique. Some of these unique genes are asthma genes, and they are handed down from parent to child, proving Hippocrates was right all along. So they now believe all cases of asthma are caused by genetics.

4. Asthma is heterogeneous. Every asthmatic presents with unique asthma signs, symptoms and triggers. What medicine works for one asthmatic may not work for another. Researchers now suspect the reason for this is due to the fact that every asthmatic has a unique combination of asthma genes.

5. Asthma genes? That’s right! Researchers have now discovered over 100 genes responsible for causing asthma, and are on the hunt to find more. They think this explains why every asthmatic is unique.

6. Some genes cause asthma. The proteins released by these genes may cause an abnormal increase in the chemicals responsible for the asthma and allergic responses. Some cause asthma by themselves, and this may explain childhood onset asthma. Others cause asthma after exposure to certain environmental triggers, and this may explain adult onset asthma. It also may explain why there are so many things that may cause asthma.

7. Some genes impact severity. Most asthmatics develop chronically inflamed air passages that are responsive to corticosteroids. However, some develop airway remodelling, such as abnormally thick airway walls, and are not responsive to corticosteroids. This might be because some asthma genes cause the inflammatory response, some cause airway remodelling, and some cause both. This might also explain why some asthmatics have mild asthma, while others have mild or severe asthma. This might also explain why some cases are easy to control with corticosteroids, and others are difficult to control regardless of the treatment.

8. Some genes cause both asthma and allergies. Some people have just asthma, but about 75 percent of asthmatics also have allergies. This might be because some genes or gene combinations cause both. Taking this a step further, some people have a perfect trifecta of asthma, allergies and eczema, causing some researchers to suspect that some genes may cause all three diseases.

9. Genetics may impact what medicine works. A common cliche among the asthma community goes something like this: “Finding what medicine works for you is often a matter of trial and error.” The theory that every asthmatic has a unique combination of genes should help explain this. Advair works great for some asthmatics, while others respond better to Symbicort. Some asthmatics respond poorly to both. As researchers learn more about how genes impact what medicine works, perhaps the day will come when a simple blood test will determine what medicine works best for you. And, of course, this may also help researchers discover better treatment options too.

10. It may lead to better categorization. As researchers learn more about human genetics, they may be able to use this information to determine what sets of genes cause what symptoms in what populations. They may be able to use this information to create more precise asthma subgroups. Perhaps a simple blood test will allow a physician to put you in one subgroup or another, and guidelines catered to that subgroup will guide your physician toward treatment options tailored just for you.

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