Your guide to eosinophilic asthma

What is eosinophilic asthma? | Symptoms | Causes | Diagnosis | Treatment | Outlook

Twenty-five million people in the United States have asthma. Five to 10% of those have severe asthma, a form of the condition that isn’t well-controlled with standard medication. Eosinophilic asthma is the most common subtype of severe asthma—a respiratory disease characterized by high levels of eosinophils, a type of white blood cell or immune cell. Never heard of it? Here’s what you need to know about this subtype of asthma and how it’s treated.

What is eosinophilic asthma?

Eosinophilic asthma is a chronic lung disease that is diagnosed when tests find high levels of eosinophils, a particular type of white blood cell, in your blood, lung tissue, and sputum—despite use of inhaled corticosteroids even at high doses. At normal levels, eosinophils are a crucial part of your immune system. They fight bacteria and ward off infections. When eosinophil levels are elevated (over 300 or 400 cells per μL), they are associated with more asthma complications, likely from induction of swelling and inflammation in your airways. 

“[Eosinophils] are protective—as well as destructive; they are foe and friend,” says Anil Mishra, Ph.D., professor of medicine and director of the Eosinophilic Disorder Center at the Tulane University School of Medicine. Higher eosinophil counts tend to be associated with more severe eosinophilic asthma disease, says Jon Romeo, DO, chair of the American College of Allergy, Asthma and Immunology (ACAAI) Asthma Committee. 

Luckily, the condition is fairly rare. The exact prevalence of eosinophilic asthma is unknown, according to the American Partnership for Eosinophilic Disorders. Some studies estimate it affects 5% of adults with asthma. Other research suggests that severe eosinophilic asthma may be more prevalent than experts have thought in the past.

Symptoms

The symptoms of eosinophilic asthma are similar to other types of asthma, but with a few added indicators. Common eosinophilic asthma symptoms can include:

• Coughing
• Wheezing
• Shortness of breath
• Chest tightness
• Inflamed nasal passages
• Nasal polyps
• Chronic sinus problems
• Lung function abnormalities

Causes

The specific cause of eosinophilic asthma is unknown. Other types of asthma (like allergic asthma) are triggered by environmental factors, including allergens such as dust mites, mold, animal fur, or pet dander. That does not appear to be the case for this type. However, it is possible that you could have allergies and eosinophilic asthma at the same time, says Dr. Romeo.

No genetic link has been pinpointed, either, although experts do note that asthma often runs in families. It’s most common in those with adult-onset asthma, rather than those who have the condition from childhood. In fact, it’s most commonly diagnosed in adults between the ages of 35 and 50 years of age. But it can occur in children, young adults, and older adults, too. 

“There is no known way to prevent asthma, outside of reducing risk—i.e., limit maternal history of smoking, living in cities, etc.,” Dr. Romeo says. “There are numerous genetic and environmental factors at play and so it is hard to know in advance who will progress to asthma and who won’t.”

How is eosinophilic asthma diagnosed?

If your asthma is severe—meaning it’s not well-controlled with inhalers and oral medications—your primary care provider will likely refer you to a pulmonologist, allergist, or immunologist for testing and diagnosis. Your healthcare provider will look for specific markers of this form of asthma, such as swollen sinuses and growths in your nasal passages. To diagnose eosinophilic asthma, there are four main tests:

1. Blood test: A blood draw can indicate high eosinophil levels—but blood eosinophil counts are not as precise for diagnosing asthma as the other tests.
2. Sputum test: You cough up a sputum sample that your provider sends for analysis or examines under a microscope. High sputum eosinophil levels indicate a positive diagnosis.
3. Bronchial biopsy: Your physician puts you to sleep then inserts a scope into your lungs to extract a tissue or fluid sample. It’s the most accurate, but the most invasive.
4. Breath test: This measures the presence of an elevated fractional exhaled nitric oxide (FENO) concentration.

If you don’t want to undergo invasive testing, your provider can also use your response to treatment to confirm a diagnosis. However, this type of asthma is often misdiagnosed as chronic obstructive pulmonary disease (COPD). Testing can help to rule out that diagnosis.

Treatment

The goal of any asthma treatment is to improve your symptoms and quality of life with as few side effects as possible. For eosinophilic asthma, that means reducing the eosinophils causing inflammation in your airways.

Medications

Some people with this type of asthma respond to traditional therapies, so your provider will likely start with:

• Inhaled corticosteroids: These are inhalers such as Flovent HFA (fluticasone) and Asmanex (mometasone) that are meant to control asthma symptoms and prevent exacerbations. Their effectiveness is based on reducing airway inflammation. If needed, they are available in combination with long-acting bronchodilators, with two examples being Advair Diskus (fluticasone-salmeterol) and Symbicort (budesonide-formoterol).
• Oral medications: These are leukotriene modifiers that suppress the inflammatory response caused by leukotrienes in your body. Examples include Singular (montelukast sodium), Zyflo (zileuton), and Accolate (zafirlukast).

Oral corticosteroids may be used short-term to reduce severe airway inflammation, but are not considered a long-term therapy for most people because they have significant side effects, according to the Asthma and Allergy Foundation of America. Your provider will assess how well your symptoms are controlled. If you’re still having persistent asthma symptoms or asthma exacerbations (aka asthma attacks), it’s time to try another treatment.

Just as Singulair targets leukotrienes to suppress the inflammation they cause, there are several biologic medications that target and thwart eosinophilic inflammation. These medications are administered via an injection or IV drip.

According to the American Lung Association, there are four appropriate options for this condition:

• Fasenra (benralizumab), a monoclonal antibody that binds to the interleukin-5 receptor (IL-5 receptor) on eosinophil cells and prevents their activation. It’s also known as an anti-interleukin-5 agent, or anti-IL-5 agent, since it blocks the action of interleukin-5.
• Nucala (mepolizumab), a monoclonal antibody blocks interleukin-5, this medication is typically used in combination with other asthma treatments for asthmatic patients 6 and older.
• Cinqair (reslizumab),  a monoclonal antibody blocks interleukin-5, this medication is an add-on treatment for patients 18 and older.
• Dupixent (dupilumab), a monoclonal antibody that is an interleukin-4 (IL-4) and interleukin-13 (IL-13) inhibitor also approved for chronic sinusitis with nasal polyps and for atopic dermatitis—making it a good treatment for people with sinus problems and eczema.

These types of medications “rapidly reduce eosinophil counts in peripheral blood in humans,” says a Frontiers in Medicine review.  

Additionally, there’s a new medication, Tezspire (tezepelumab-ekko) that was approved in December 2021. According to the manufacturer, it’s “the first and only biologic for severe asthma that does not have a phenotype—eosinophilic or allergic—or biomarker limitation within its approved label.” It’s a  thymic stromal lymphopoietin (TSLP) antagonist that targets the action of a cytokine that contributes to inflammation. It is taken by injection, once every four weeks. 

Additionally, Xolair (omalizumab), a biologic originally approved for allergy-induced asthma may be useful for some people with eosinophilic asthma. Research has shown that it can reduce blood eosinophil levels.  

Lifestyle changes

There aren’t any natural treatments or home remedies that will effectively cure asthma on their own. “However, for people with allergic-triggered asthma, avoiding their triggers or considering a course of allergy shots can be helpful to reduce and sometimes eliminate symptoms,” says Dr. Romeo. Additionally, with appropriate medication the following may help to reduce symptoms for some asthma patients:

• Exercise, such as yoga
• Breathing techniques
• Caffeine
• Weight loss

Outlook

One of the risks of severe eosinophilic asthma is the potential for airway remodeling, or scarring, and damage to the lungs that can occur over time. As a 2019 review in the Journal of Clinical Medicine cautions: “Persistent inflammation caused by eosinophils leads to constant damage of the airways.” Once airway remodeling occurs, it is a lot harder to reverse asthma symptoms, explains Dr. Romeo. And that can have a very detrimental effect on a person’s quality of life. Proper treatment can help to prevent this.

You can get very good asthma control with the biologic therapies that are now available. These medicines have been real game-changers. “I have people who have struggled for years,” Dr. Romeo says. “We get them on [a biologic therapy], and they come back in and say they’re working out again or they’re playing with their grandkids or going to work or traveling.” 

And if you haven’t found the one that gives you perfect symptom control, more will certainly come along, down the road. For example, while IL-5 is well-known for its association with eosinophilia, another cytokine may be a target for future treatments, says Dr. Mishra. According to a paper that he co-authored for the journal Allergy in 2021, animal studies have shown potential benefits in targeting the IL-18 pathway. His research suggests that “anti-IL-18 neutralization (could be) a novel immunotherapy to restrict asthma pathogenesis.” Plus, it could target only the pathogenic eosinophils and leave alone the other ones needed to help the immune system function. 

Ultimately, you want to find an asthma treatment that allows you to have the quality of life that you desire. Work with your provider to find the right combination of medications for you—or ask about clinical trials for newer medications that are in development.