Asthma: Causes | Symptoms | Diagnosis | Treatment

Asthma is a long-term non-communicable disease that affects your lungs by narrowing and swelling your airways. This condition causes overproduction of mucus, leading to coughing, wheezing (whistling sounds from the chest) and shortness of breath. Asthma is a minor irritation for some people, while it may affect daily activities in others and may lead to a fatal asthma attack.

Highlights

• Asthma is a long-term non-communicable disease that affects your lungs by narrowing and swelling your airways.
• Asthma causes overproduction of mucus, leading to coughing, wheezing (whistling sounds from the chest) and shortness of breath.
• Common asthma symptoms include coughing, wheezing, shortness of breath, and tight chest and chest pain.
• Treatment of asthma includes bronchodilators, anti-inflammatory medicines and biological therapy for asthma.

What is asthma?

Asthma is a long-term lung disease in which tightness and swelling of airway muscles lead to inflammation and irritation, making breathing difficult. Even asthma affects your routine activities, such as communication and movement. Asthma is also called “chronic respiratory disease” or “bronchial asthma” (Figure 1).

The characteristic cause of asthma is inflammation and overproduction of mucus in your bronchial tubes, and it has three primary symptoms, such as:

Airway obstruction: The muscles surrounding your airways relax when you breathe normally, allowing air to flow freely. However, the muscles tighten when you have asthma, so air hardly passes through the muscles to reach lung cells.

Inflammation: Bronchial tubes in asthma patients are red and swollen, which means inflamed. Your lungs may suffer from this inflammation, and its treatment is the key to long-term asthma management.

Airway irritability: Asthmatics have sensitive airways that naturally tend to overreact and constrict in response to mild triggers.

Characteristic features of an asthma attack include bronchospasm, inflammation and mucus secretion. When your airway muscles constrict, air cannot pass through them, called bronchospasms that swell your airway linings and lead to inflammation that causes excessive mucus secretion in the airways. So, all these characteristics collectively cause an asthma attack.

Classification of asthma

1. Intermittent mild asthma: If you feel mild asthma symptoms once a week and once a month at night.
2. Persistent mild asthma: If you feel mild asthma symptoms 3-6 times a week and 3-4 times a month at night, that might affect your activities.
3. Persistent moderate asthma: If you daily feel symptoms of asthma with multiple nocturnal asthma attacks in a month.  
4. Persistent severe asthma: If you have ongoing signs and symptoms of asthma that appear day and night and that restrict your activities.

Types of asthma

The main types of asthma include allergic, non-allergic, adult, childhood, exercise-induced, occupational, and asthma-COPD overlap syndrome (ACOS).

1. Allergic asthma commonly occurs due to allergens such as pollens, some types of molds, and pet dander.
2. Non-allergic asthma occurs due to factors other than allergens such as stress, illness, weather etc.
3. Adult-onset asthma commonly occurs in adults before age 50 but after 18 years.
4. Childhood asthma occurs in children before the age of five years and occasionally requires an asthma inhaler.
5. Exercise-induced asthma occurs due to physical exercise.
6. Occupational asthma is more common in industrial workers due to certain chemicals and fumes.
7. Asthma-COPD overlap syndrome (ACOS)
8. Asthma-COPD overlap syndrome (ACOS) occurs when chronic obstructive pulmonary disease and asthma happen simultaneously as they both cause difficulty breathing.

Causes

It is still unknown why asthma occurs in some people while not in others. However, certain factors trigger or induce asthma in some people, including exposure to allergens such as pollens, environmental factors such as chemicals and fumes, or familial genetic factors.

How does asthma happen?

When an asthmatic person inhales and is exposed to allergens such as pollens or dust mites, the lung cells release chemicals known as chemoattractants. These chemicals stimulate and activate the lung immune system that allergens as foreign particles of extreme severity. Consequently, numerous immune system cells, such as neutrophils and eosinophils, travel to the affected site and degranulate to release cytotoxic chemicals that destroy the foreign particles. These immune system cells also do phagocytosis and cause opsonization by activating the complement system. All these factors constrict lung airways and release excessive cytotoxic chemicals to induce inflammation which causes a localized inflammation in the lungs and airway tightening. Thus, asthma patients cannot inhale much air, and suffocation occurs in the lungs, a life-threatening condition requiring prompt medical treatment, or death may occur.

Symptoms

Common asthma symptoms include coughing, wheezing, shortness of breath, and tight chest and chest pain (Figure 1).

Diagnosis

Your healthcare provider will collect your medical history, mainly related to history, to identify the familial origin of asthma, previous onsets of allergy to allergens and previous lung disease (if any). Doctors commonly order a spirometry test that measures airflow through your lungs to detect breathing problems and monitor treatment progress. If your symptoms and spirometry test cannot diagnose asthma, you may have a methacholine test and exhaled nitric oxide test. In the methacholine test, you inhale methacholine allergen before and after spirometry to analyze if methacholine is tightening your lung airways or not. Whereas exhaled nitric oxide test measures the amount of nitric oxide that your lungs exhale. The human body typically produces nitric oxide gas, and high levels of exhaled nitric oxide show inflamed airways.

Similarly, chest X-rays, skin tests and blood tests are other options to diagnose lung problems, including asthma.

Treatment

Dilators, anti-inflammatory medicines and biological therapy for asthma.

• Dilators: Different medicines such as bronchodilators, theophylline, short- and long-term beta-agonists and anticholinergics dilate your airway muscles and ease your breathing. Sometimes, beta-agonists can be used in combination with corticosteroids, which are long-term treatments for asthma. Corticosteroids help recover your airway swelling and excessive mucus secretion.
• Anti-inflammatory medicines such as leukotriene inhibitors or blockers reduce inflammation in your lungs.
• Doctors recommend biological therapy if your body is not responding to asthma medicines. Biological therapy includes medications that reduce and stop immune system response against different allergens, thereby inhibiting lung inflammation.