If you have asthma, there’s a good chance someone else in your family does too. Genetics are among the major causes of asthma, a common but complex disease that is likely influenced by a combination of factors.
Asthma affects the airways and lungs, making it hard to breathe and causing symptoms such as coughing, wheezing, and shortness of breath. About 1 in 13 people in the United States have this chronic (long-term) condition.
Even though so many children and adults have asthma, it isn’t clear why some people develop it and others don’t. Research suggests that you’re more likely to have asthma if a member of your family does, but there isn’t one single gene that causes asthma. Also, a mix of environmental and genetic factors appear to play roles in the development of asthma.
Researchers studying the epidemiology (frequency and causes) of asthma discovered that the disease runs in families. Findings of a 1998 study showed that children who had one or two parents with asthma were three to six times more likely to develop it than someone without a family history of asthma.
In a 2015 study in the European Clinical Respiratory Journal, researchers reported that a person who is not related to anyone with asthma has about a 5 percent risk of developing asthma. Children with one parent with asthma have a 25 percent risk, which rises to 50 percent if both parents have it. Having a sibling, aunt, uncle, niece, or nephew with asthma also increases risk. A family history of asthma is also associated with earlier onset and more severe disease, the study authors said.
Studies on identical twins, who share the same genes, have allowed researchers to better understand the extent of genetic factors in asthma development. Scientists estimate that genetics account for 60 percent to 80 percent of a person’s chances of developing asthma.
Scientists have used genome-wide association studies (a method that examines the DNA of a large group of people) variants in the genetic code — called single nucleotide polymorphisms — that most often occur in people with asthma. More than 100 genes are associated with allergic asthma, the most common form of the condition.
The genes associated with asthma tend to be involved with the immune system, lung and airway structure, and lung function.
Asthma is caused when the immune system overreacts to certain triggers, such as:
An overreactive immune system can cause inflammation in the lungs and airways, which can make breathing difficult and can trigger an asthma attack. The inflammatory response in allergic asthma is linked to increased levels of an immune protein called the immunoglobulin E (IgE) antibody.
IgE antibodies are part of your body's normal response to a foreign invader — they alert your immune system to launch an attack to keep you healthy. In people with allergic asthma, the body makes IgE antibodies in response to allergens, causing inflammation and making the airway hyperreactive.
Scientists have noticed an association between potential asthma genes — called candidate genes — and the genes involved in this immune system response.
For example, mutations (changes) in a protein called filaggrin are linked with greater sensitization to allergens and higher IgE antibody levels. Filaggrin is involved in maintaining the skin barrier. When this protein is mutated, people may be more susceptible to developing allergies, eczema, and asthma.
Long-term airway inflammation in people with poorly controlled asthma can cause airway remodeling — structural changes to airways and lungs that make it even harder to breathe. This process happens slowly over time, causing the airway walls to thicken and airways to narrow. These structural changes can be permanent and decrease lung function.
Scientists have found several genes associated with decreased lung function in people with asthma. One gene, ADAM33, makes a protein in some of the cells responsible for lung and airway structure. Studies suggest that this protein and gene may contribute to inflammatory response and airway remodeling.
Studies on the genetic cause of asthma also make it clear that family history isn’t the only factor in your susceptibility to asthma. Environmental factors play a large part.
Only about 75 percent of identical twins develop asthma if their twin has it. If genetics alone caused asthma, the proportion would be 100 percent because identical twins share the exact same genes.
Additionally, the disease occurs in people who don’t have a family history of asthma. Other risk factors that can contribute to the development of asthma include:
You may wonder if there is a way to prevent asthma if you have a family history, or you might worry about passing asthma on to your children if you have it. It’s not always possible to prevent asthma, but research shows that you can take steps that may decrease your risk. For example, you can:
No matter the cause — genetic or otherwise — if you or your child develops asthma, talk to your asthma care team. They can help you find the best asthma treatment that will lead to optimal quality of life.
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