Eosinophilic Asthma

Eosinophilic asthma (also known as e-asthma or eos asthma) is a severe form of asthma that causes high levels of eosinophils in the lung tissue, blood, and mucus. Eosinophils are a type of immune system cell that typically help your body fight infections. Too many of these cells can cause inflammation in your airways and worsen asthma symptoms.

Eos asthma typically develops in adulthood, though it can also affect children. While the exact cause of eos asthma remains under investigation, genetic and environmental factors likely play a role in its development.

This type of asthma doesn't respond to traditional treatments, so other management techniques are necessary. Targeted therapies, such as biologics, are essential for managing symptoms and preventing asthma attacks and other complications of eos asthma.

Eosinophilic Asthma Symptoms 

People with eosinophilic asthma experience classic asthma symptoms, though they tend to be more persistent and severe than other asthma types. However, this type of asthma also causes inflammation that can narrow the airways and decrease your lung function—meaning, your lungs can't hold as much oxygen as they normally would. That said, common symptoms associated with this type of asthma include:

• Wheezing: A high-pitched whistling sound when breathing
• Coughing: A persistent, dry cough that may worsen at night or with exercise
• Shortness of breath: Difficulty catching your breath
• Chest pain: A feeling of tightness or pressure in the chest, making breathing uncomfortable
• Chronic rhinosinusitis: Chronic inflammation and swelling of the sinuses, which can cause nasal drainage, nasal blockage, facial pressure or pain, and a decreased sense of smell
• Nasal polyps: Soft growths that develop on the lining of the sinuses or nose, causing stuffiness, runny nose, loss of smell or taste, sneezing, and snoring
• Difficulty sleeping: Worsening symptoms at night, leading to difficulty falling or staying asleep
• Fatigue: Feeling tired or lethargic in the daytime due to disrupted sleep or difficulty breathing
• Exercise intolerance: Difficulty engaging in physical activity due to experiencing asthma symptoms during exercise
• Frequent respiratory infections: Impaired lung function can increase the risk of developing respiratory infections (like the common cold)

Because high levels of eosinophils cause chronic airway inflammation, people with eos asthma are at a higher risk of experiencing asthma attacks—which are periods when asthma symptoms worsen. If you develop an asthma attack, common symptoms include:

• Coughing
• Increased wheezing
• Chest pain or feeling as though a heavy weight is sitting on your chest 
• Difficulty catching your breath, as if you are sucking air through a straw 
• Gasping for air 
• Retractions, which occur when your ribs pull in with each breath
• Neck pain as a result of your muscles tightening if you're having trouble breathing strain to breathe

Causes

Eosinophilic asthma develops when abnormally high levels of eosinophils cause inflammation in the entire respiratory tract, from the sinuses to the small airways in the lungs. Eosinophils are white blood cells that play an important role in the immune system, helping your body release inflammatory chemicals that fight infections.

An overactive immune response can increase eosinophil production, causing inflammation that narrows the airways, increases mucus production, and leads to hallmark asthma symptoms. Over time, inflammation can damage the airways and lung tissue, worsening asthma symptoms.

Researchers don’t know exactly what causes high levels of eosinophils and eosinophilic asthma, but genetic and environmental factors likely play a role. 

Genetics 

Studies about how genetics may be associated with eosinophilic asthma are ongoing. However, researchers have discovered some inherited gene mutations (changes) that may increase your risk of developing this condition.

Changes in genes that regulate the production and function of eosinophils may increase eosinophil counts in the blood and promote the buildup and activation of eosinophils in the airways. This can lead to inflammation and an increased risk of eosinophilic asthma.

Environmental Triggers 

Some people with eosinophilic asthma also have allergic conditions, such as hay fever, eczema, or food allergies. This doesn't apply to everyone who has asthma. However, if you do experience allergies, the following environmental factors can trigger or worsen eos asthma symptoms:

• Pollen
• Pet dander
• Dust mites
• Mold spores
• Lung irritants, like smoke or cleaning chemicals
• Strenuous exercise 
• Respiratory illnesses (e.g., the common cold, influenza)
• Extreme weather 
• Stress

Risk Factors 

While genetics and environmental factors can play a role in the development of eos asthma, other factors can also increase your risk of this condition. Consider the following:

• Being 35-50 years old
• Having a personal or family history of asthma or other allergic conditions
• Smoking tobacco
  

Diagnosis

If you have severe asthma or your asthma symptoms do not improve with standard treatments, your healthcare provider may order tests to determine whether you have eosinophilic asthma. During your appointment, your provider will consider your symptoms, medical history, and test results to provide an accurate diagnosis. They can also order additional tests to confirm a diagnosis, including:

• Blood test: Blood tests measure your eosinophil count—the amount of eosinophils circulating in your blood. People with eosinophilic asthma have an eosinophil count of 150 cells or more per microliter of blood (cells/μl). Other types of asthma can also cause elevated eosinophil counts, so your healthcare provider will consider your symptoms and other test results.
• Sputum test: The provider collects a sample of coughed-up mucus (sputum) and examines it under a microscope to measure eosinophil cells in the sample. If you cannot bring up mucus when coughing, your provider may ask you to breathe in a saline solution through a nebulizer. In people with eosinophilic asthma, more than 2% of the cells within sputum will be eosinophils. 
• Bronchial biopsy: A pulmonologist (a doctor specializing in lung diseases) will insert a thin tube called a bronchoscope into your nose or mouth to access your lungs. They will collect a sample of tissue or fluid and view it under the microscope to look for eosinophils and signs of inflammation. 

Eosinophilic Asthma Treatment 

If you receive a diagnosis for eos asthma, your healthcare provider will help you develop a treatment plan that meets your needs. The goal of treatment is to reduce eosinophils in the airways, control inflammation, improve asthma symptoms, and reduce the frequency and severity of asthma attacks.

Most people with eosinophilic asthma respond well to traditional asthma treatments but require some biologic medications directed against eosinophils or cytokines that regulate eosinophil growth and development.

Standard Asthma Treatments

First-line treatments for eos asthma are the same medications healthcare providers use to treat other types of asthma. These include:

• Bronchodilators: Inhaled medicines that relax the muscles around the airways to open them and relieve symptoms like coughing, chest tightness, and wheezing. For example, short-acting beta-2 agonists (SABAs) provide quick relief when symptoms worsen, while long-acting beta-2 agonists (LABAs) help keep airways open for longer periods. Muscarinic antagonists are other bronchodilators that can be short-acting (SAMAs) or long-acting (LAMAs).
• Corticosteroids: Powerful anti-inflammatory drugs that help reduce airway inflammation. 
  
• Leukotriene modifiers: Oral medications that block the action of leukotrienes—inflammatory immune chemicals that are involved in your body’s immune response to allergens. These medicines help reduce airway swelling in people with eos asthma and allergies. 

Biologics

Healthcare providers prescribe biologic medications for people with eos asthma when traditional asthma treatments are ineffective. Your healthcare provider may prescribe biologic drugs via subcutaneous injections (under the skin) or intravenous administration (through a vein in your arm). 

In most cases, your healthcare provider will likely recommend that you continue taking traditional asthma medications alongside biologics. There are four FDA-approved biologic therapies for treating eos asthma, including:

• Fasenra (benralizumab): Prevents inflammatory cytokine interleukin-5 from activating eosinophils to reduce eosinophil counts and airway inflammation
• Nucala (mepolizumab): Binds to interleukin-5 to decrease eosinophil counts in your blood and reduce airway inflammation
• Cinqair (reslizumab): Lowers eosinophil counts in the blood and reduces airway inflammation by binding to interleukin-5 to control eosinophil production
• Dupixent (dupilumab): Binds to inflammatory cytokine interleukin-4 receptors to reduce airway inflammation

How To Prevent Eosinophilic Asthma

While there is no known way to prevent eosinophilic asthma from developing, several strategies can help reduce the frequency and severity of symptoms and asthma attacks. These include the following:

• Avoid triggers: Identify and avoid triggers that worsen your asthma symptoms. It may help to keep a symptom journal and write down your activities, foods you eat, and other potential environmental triggers. Common triggers include dust mites, pollen, cigarette smoke, strenuous exercise, and emotional stress. 
• Follow your treatment plan: Take your asthma medications as prescribed and maintain regular follow-up appointments with your healthcare provider to ensure your medications are working and your eos asthma is well-controlled. 
• Track your asthma: Use a peak flow monitor (a tool that measures how well air moves in and out of your lungs) to identify changes in your breathing before asthma symptoms appear. Using a peak flow monitor daily can help monitor treatment effectiveness, track changes in your breathing over time, and prevent asthma attacks.

Related Conditions

People with eosinophilic asthma often have other conditions that develop in response to overactive immune responses or high eosinophil counts. These include:

• Chronic rhinosinusitis with nasal polyps: Up to 60% of people with eos asthma have chronic rhinosinusitis with nasal polyps. Chronic sinus inflammation and polyps (soft growths) in the nasal passages cause a stuffy or runny nose, decreased sense of smell, facial pressure or pain, headaches, pain in the upper teeth, and snoring. 
• Allergic rhinitis: Also known as hay fever, allergic rhinitis is inflammation of the nasal passages in response to allergen exposure. Many people with eos asthma also have allergic rhinitis, as both conditions involve an overactive immune response and airway inflammation.
• Eosinophilic esophagitis: A chronic inflammatory condition that develops when eosinophils inflame and irritate the esophagus, leading to symptoms like difficulty swallowing, heartburn, acid reflux, and chest pain.

Living With Eosinophilic Asthma

It can be challenging to live with eosinophilic asthma. When your symptoms are poorly controlled, you may have trouble participating in your daily activities, including work, school, and hobbies. Fortunately, leading a fulfilling, active life with the right treatments and support is possible with eos asthma. 

Adhering to your treatment plan and close communication with your healthcare provider is the best way to keep your asthma well-controlled. Seeking support from healthcare providers, support groups, and loved ones can also provide valuable emotional and practical support.