Asthma

Asthma is a chronic inflammatory respiratory disease that manifests itself in repeated obstruction of the airways. The chronic inflammation is a result of heightened sensitivity to certain trigger substances, which leads to airways obstruction due to greater production of mucus and increased contraction of the smooth muscles in the bronchus (bronchospasm). Asthma is a heterogeneous disease with various different aetiologies, triggers, signs and symptoms and responses to treatment. It’s an important health problem, as it’s the most frequent type of chronic lung diseases, affecting around 400 million people around the globe. The number of asthmatic patients is increasing, especially in the countries with low-to-moderate income.

Long-term control of asthmatic symptoms involves lowering the inflammatory response by avoiding environmental triggers, taking anti-inflammatory drugs and managing associated conditions that may make asthma worse.

Causes

The exact cause for asthma isn’t entirely known. Research attributes it to a combination of environmental factors and the genetic predisposition of an individual. It’s assumed that asthma appearing before the age of 12 is due more to genetic factors, while environmental factors play a greater role in asthma that appears later in life.

Asthma is also closely connected to allergic rhinitis. Allergic rhinitis affects as much as 20-30% of the world population, and asthma develops in nearly half of the patients. The appropriate treatment of allergic rhinitis is an important step in preventing asthma, nasal polyps and the loss of smell.

Genetics

Asthma develops more frequently in individuals with family history of the illness. There are a number of genes responsible for asthma, most of them connected to the development of the immune system, the synthesis of cytokines (proteins secreted by certain immune cells during an immune response) and the regulation of other inflammatory mechanisms. The expression of these genes is likewise influenced by the environment and the age at which one is exposed to environmental factors as a child.

Environment

It’s proven that smoking during pregnancy and after birth increases the risk of asthma in the child. Other risk factors include virus infections (especially those causing pneumonia or bronchiolitis: rhinoviruses, RSV, influenza virus, parainfluenza virus and adenovirus) in early childhood, air pollution, atopy and the sensitization to food or inhaled allergens.

Cold and dry air, strong smells and quickened breathing due to physical exercise don’t cause asthma but only trigger bronchospasms in people who already have the illness. These triggers worsen the inflammation in the affected individual, which leads to increased production of mucus and, at the same time, increases bronchospasms.

Pathogenesis

In smaller airways, the airflow is regulated by smooth muscles that surround the lumen of the airways. During an asthmatic episode, the airways become inflamed due to environmental triggers, which leads to the contraction of smooth muscles and thus to the direct and, in some cases, even a complete closure of the airflow. Aside from bronchoconstriction, the already constricted airways can be further blocked by increased secretion of mucus, which triggers coughing and other breathing difficulties. Due to the chronic course of asthma, patients typically have damaged epithelium, thickened basement membrane (with typical eosinophilic infiltration) and hypertrophy of smooth muscles. The inflammatory process maintains the levels of helper T cells and other immune cells that produce anti-inflammatory cytokines . Bronchospasms can resolve spontane (IL-4, IL-5, IL-13)ously or through therapy. However, in 50% of cases, they become a part of a late response that follows the first one after 3 to 12 hours and takes the form of repeated bronchoconstriction and inflammation.

Triggers

Environmental allergens

typically inhaled allergens (mittens, pollen, mould spores, epithelial cells from pets)

Air pollution

with reactive organic substances (perfumes, scented soap, detergents, hair sprays, deodorants, air fresheners, etc.), cigarette smoke

Drugs

aspirin, beta blockers, ibuprofen, penicillin – especially in adults

Food

milk, nuts, eggs – usually also trigger other atopic conditions together with asthma

Sulphur compounds

often found in wine as preservatives

Fossil fuel products

air pollution with fossil fuel products (smog, ozone, nitrogen dioxide, sulphur dioxide) – probably one of the leading causes for the increased prevalence of asthma in urban environments

Monochloramine

chlorinated water in swimming pools

Virus infections

the most frequent triggers of asthma in children

Exercise

probably due to the increased exposure to cool, dry air

Psychological stress

including laughter

Signs and symptoms of asthma

Asthmatic patients experience occasional, repeated dry cough with wheezing and breathing difficulties. Older children and adults experience shortness of breath, while younger patients distinctly complain of chest pain. Symptoms are worse at night, especially in the presence of respiratory infections and allergens. The symptoms can also appear during physical exertion, hyperventilation and cold and dry air. You are more likely to be diagnosed with asthma if you also suffer from allergic rhinitis, allergic conjunctivitis and atopic dermatitis and have a confirmed family history of asthma.

There are two types of asthma in children that manifest in the following ways:

a) repeated episodes of wheezing in early childhood that are primarily triggered by respiratory viruses infections and disappear in the pre-school or school period.

b) chronic asthma connected to allergies and persisting in late childhood and even adulthood.

 

Treatment

The goals of treating asthma are to improve the bothersome symptoms, preserve normal physical activity and the ability to continue with one’s schooling and prevent future episodes of asthmatic attacks.

Drugs for treating asthma are divided into two groups:

a) long-acting drugs (blockers or anti-inflammatory drugs)

  • inhaled glucocorticosteroids,
  • long-acting beta agonists,
  • theophylline,
  • IgE monoclonal antibodies.

b) short-acting drugs (used for relieving symptoms)

  • short-acting beta agonists,
  • anticholinergics.

Viri

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  8. Asher M.I. , Montefort S. , Bjorksten B., Ali C.K., Sreachan D. P., Weiland S.K., Williams H., ISAAC Phase Three Study Group.   Worldwide time trends in the prevalence of symptoms of asthma, allergic rhinoconjunctivitis, and eczema in childhood: ISAAC Phases One and Three repeat multicountry cross-sectional surveys. Lancet, 368 (9537): 733-743.