Asthma (Johansson, 2019) – Is asthma genetic?

lung diorama

Nebula Genomics DNA Report for Asthma

Is asthma genetic? We created a DNA report based on a study that attempted to answer this question. Below you can see a SAMPLE DNA report. To get your personalized DNA report, purchase our Whole Genome Sequencing!

A sample report on asthma from Nebula Genomics
A sample report on asthma genetic variants from Nebula Genomics

Additional Information

What is Asthma? (Part 1 of Is asthma genetic?)

Asthma is a chronic, inflammatory disease of the airways with permanent hypersensitivity. In certain individuals, the inflammation may lead to the acute airway narrowing of bronchial obstruction. This airway narrowing is caused by increased secretion of mucus, spasm of the bronchial muscles, and formation of edema of the bronchial mucosa. A variety of stimuli causes the increase in airway sensitivity and associated inflammation, but the condition is reversible with treatment.

A distinction is made between allergic (extrinsic) asthma and non-allergic (intrinsic) asthma. In pure form, however, these occur in only about ten percent of patients; mixed forms are observed in the majority. While the allergic version is more common in children, the non-allergic form is more frequent in old age. Prenatal cigarette smoke exposure seems to promote asthma. There is also evidence that cultural and civilizational circumstances, as well as certain drug applications in early childhood, promote asthma.

Healthy and asthma lungs
Asthma changes how much air can pass through the lungs. Wikipedia. CC-Attribution-Share Alike 4.0 International.

Allergic asthma

Allergies and asthma are often seen together. Allergic exogenous asthma is triggered by external stimuli (allergenic substances in the environment, so-called allergens) if there is a corresponding genetic predisposition to atopy (the genetic tendency to develop allergic diseases). Type E immunoglobulins (IgE) are formed which, in interaction with specific allergens, cause the release of allergy-triggering messenger substances such as histamine, leukotrienes and bradykinins from mast cells. These substances then trigger airway constriction. A delayed reaction can occur after 6 to 12 hours, triggered by type G immunoglobulins (IgG). Often both reactions occur.

Non-allergic asthma

Non-allergic asthma can be caused by other stimuli: Infections, usually of the respiratory tract, drug intolerances, usually towards nonsteroidal anti-inflammatory drugs such as acetylsalicylic acid), drug side effects (e.g. of beta-receptor blockers and cholinesterase inhibitors), exposure to toxic or irritating substances, special physical exertion, and reflux disease are possible causes of this form. Some correlations and other causes are not yet clear.

Three characteristics of all asthma cases include:

  • Inflammation of the bronchial tubes: Allergens or other stimuli trigger an inflammatory reaction of the bronchial mucosa. 
  • Bronchial hyperreactivity: Hyperreactivity can often be felt when inhalation of irritant substances occurs, during exercise, or by cold air provocation. Substance P, a neuropeptide detected in the respiratory tract, is thought to be involved in the pathogenesis of bronchial hyperreactivity.
  • Lack of bronchial clearing: Obstruction is the narrowing of the airway due to mucosal edema (fluid retention in the mucosa), increased or impaired mucus secretion, and bronchospasm. As a result, self-cleaning of the lungs is reduced. Secretions cannot drain and, in turn, increase damage to the point of obstruction, known as bronchial effusions.

Epidemiology (Part 2 of Is asthma genetic?)

According to the Centers for Disease Control and Prevention (CDC), 7.7% of all U.S. adults and 7.5% of U.S. children younger than 18 years had some form of asthma in 2018. The condition is more common in boys under 18 than girls (8.3% and 6.7%) but more common in adult women (9.8%) than adult men (5.5%). 

The condition is slightly more prevalent in black and hispanic than in other populations.

Symptoms (Part 3 of Is asthma genetic?)

Symptoms of asthma vary in both frequency and severity among individuals. Some common symptoms include:

  • coughing or wheezing
  • chest tightness
  • difficulty breathing
  • shortness of breath
Pathology of asthma
In asthma, the airways become restricted. Pixy.org. CC-NonCommercial-NoDerivatives 4.0 International.

People with asthma may experience a short period of worsening symptoms called an asthma attack. In an attack, there is acute shortness of breath and constriction of the bronchial tubes. Exhalation in particular is difficult and is often accompanied by whistling breath sounds. In some cases, coughing occurs in the form of coughing fits. In children, cough is usually the leading symptom. Difficulty breathing and shortness of breath can lead to feelings of anxiety with restlessness, difficulty speaking, and nausea.

Causes (Part 4 of Is asthma genetic?)

Both genetic and environmental factors contribute to asthma. It tends to occur in individuals with a family history and thus genetics play an important role in causing asthma. But environmental factors may also play a key role.

Is asthma genetic?

In allergic asthma, it was observed that children of parents who both suffer from allergic asthma have a 60-80% risk of developing the disease. According to a CDC report, if a person has a parent with asthma, they are three to six times more likely to develop the condition than someone who does not have a parent with asthma. This condition is a complex heritable disease and it is believed that a combination of gene mutations contribute to the chances a person will develop it.

Environmental factors

Development of allergies (which also run in families) or respiratory infections tend to increase a person’s risk of developing asthma. Additional risk factors include exposure to certain allergens or chemicals in the environment may trigger the condition, including occupational asthma acquired through the workplace. 

Environmental and health triggers that increase the risk of asthma include:

  • Respiratory infections, including the cold or flu
  • Irritants in the air
  • Air pollution
  • Tobacco smoke
  • Exercise induced asthma
  • Cold air
  • Medications, including beta-blockers and nonsteroidal anti-inflammatory drugs
  • Stress
  • Food and drink preservatives
  • Allergic reactions, including dust mites, dander, and pollen
  • Acid reflux
  • Hay fever
Asthma triggers
Many environmental factors trigger asthma. Wikipedia. CC-Attribution-Share Alike 3.0 Unported.

Other diseases, such as Eosinophilic granulomatosis with polyangiitis, are associated with the immune system and play a role as precursors of the condition.

Diagnosis (Part 5 of Is asthma genetic?)

Diagnosis is often easy to make with a history of the main symptoms.

According to Mayo Clinic, diagnosis is aided by lung function testing to test how much air moves in and out as you breathe. 

A spirometry test measures the total volume of air inhaled and exhaled and the volume exhaled in one second during forced exhalation (a measurement of how fast you can exhale). The ratio of these two measurements is used to indicate airway constriction.

The PEF value (peak expiratory flow) is also used for diagnosis and therapy monitoring and is a measure of how hard you can breathe out. This value usually decreases even before an asthma attack. It is measured with a “peak flow meter,” which is available in a variety of age-adapted designs.

These tests are often done before and after taking a medication to open your airways called a bronchodilator. If your lung function improves with use of a bronchodilator, it’s likely you have asthma.

Other tests that help diagnose the condition are:

  • Methacholine challenge: Methacholine is a known asthma trigger. When inhaled, it will cause your airways to narrow slightly. If you react to the methacholine, you likely have asthma. 
  • Imaging tests: A chest X-ray can help identify any structural abnormalities or diseases (such as infection) that can cause or aggravate breathing problems.
  • Allergy testing: Allergy tests can be performed by a skin test or blood test. 
  • Nitric oxide test: When your airways are inflamed, you may have higher than normal nitric oxide levels. This test isn’t widely available.
  • Sputum eosinophils: This test looks for certain white blood cells (eosinophils) in the mixture of saliva and mucus (sputum) you discharge during coughing. 
  • Provocative testing for exercise and cold-induced asthma: In these tests, your doctor measures your airway obstruction before and after you perform vigorous physical activity or take several breaths of cold air.

Determining how severe a patient’s condition is helps medical professionals recommend treatment. Severity is classified based on symptoms as mild intermittent (mild symptoms up to two days a week and up to two nights a month), mild persistent (symptoms more than twice a week, but no more than once in a single day), moderate persistent (symptoms once a day and more than one night a week), or severe persistent (symptoms throughout the day on most days and frequently at night).

Treatment (Part 6 of Is asthma genetic?)

In most cases, asthma medicine comes as either an inhaler or a nebulizer, which delivers medicine directly to the lungs. Other asthma treatments are in pill form. The Asthma and Allergy Foundation of America provides health information and asthma action plans on their website.

There are two types of inhalers for treating asthma: metered dose inhaler (MDI) and dry powder inhaler (DPI). MDIs deliver an aerosol while DPIs deliver dry powder. 

A patient using an inhaler
An inhaler helps deliver asthma medication directly to the lungs. Wikipedia. CC-Attribution-Share Alike 4.0 International

A nebulizer converts liquid into a mist that you inhale through a tube. It is most often recommended for patients who have difficulty using inhalers. 

Options for a long term treatment plan include:

  • Inhaled corticosteroids to prevent and reduce airway swelling and reduce mucus in the lungs. They are the most effective long-term control medicines available. 
  • Inhaled long-acting beta agonists open the airways by relaxing the smooth muscles around the airways.
  • A combination of inhaled corticosteroids and inhaled long-acting beta agonists
  • Biologics (shots or infusions given every few weeks) target a cell or protein in your body to prevent airway inflammation. They can be very expensive treatments and are usually only prescribed when other treatments fail.
  • Leukotriene modifiers are taken in pill or liquid form. This type of medicine reduces swelling inside the airways and relaxes smooth muscles.
  • Cromolyn sodium is an inhaled non-steroid medicine. It prevents airways from swelling when they come into contact with an asthma trigger.
  • Theophylline comes as a tablet, capsule, solution and syrup to take by mouth. This medicine helps open the airways by relaxing the smooth muscles.
  • Oral corticosteroids are taken in pill or liquid form. 

Quick relief medicine is available for when immediate relief is needed. These medicines act fast to relax tight muscles around your airways and allow the airways to open up. 

  • Short-acting beta agonists are inhaled. They are the first choice for quick relief of asthma symptoms.
  • Long-acting muscarinic antagonists (LAMA) or anticholinergics are inhaled but act slower than the short-acting beta agonist medicines. 
  • A combination of short-acting beta agonists and long-acting muscarinic antagonists (LAMA). 

Asthma is a chronic condition that is controllable, but not curable. Treatment depends on the frequency and severity of the symptoms. Additionally, treatment may change if symptoms change. While medicine is helpful for reducing symptoms, patients tend to get the best treatment when they both take medicine and avoid triggers.

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