What is Eosinophilic Asthma?
While some people may think of asthma as one disease, there are actually many different types of asthma. One type that tends to more severe and harder to control is eosinophilic asthma (EA).
What is eosinophilic asthma?
Eosinophilic asthma is a subtype of asthma that has been recognized for more than 100 years. It usually develops in adulthood and tends to be a severe form of asthma. It can be hard to control because it does not respond to treatment with high doses of oral corticosteroids like other forms of asthma.1,2
Eosinophilic asthma impacts the whole respiratory tract, from the sinuses to the small, or distal, airways deep in the lungs. People with EA are often diagnosed with nasal polyps and chronic sinus disease too.
What are eosinophils?
Eosinophils are a type of white blood cell that plays two roles in the immune system: they destroy foreign substances and regulate inflammation. If too many eosinophils congregate in certain tissues, it can cause a host of inflammatory-based conditions, such as asthma, eczema, Crohn’s disease and certain types of cancer.3
With eosinophilic asthma, the number of eosinophils overpopulates the blood, lung tissue, and mucus (sputum) in the respiratory tract. This causes the airways to swell and become narrow, making it hard to breathe. Research has shown that higher levels of eosinophils in the blood is linked to severe asthma attacks in the future.
Who can get eosinophilic asthma?
Eosinophilic asthma is most often diagnosed in adults between the ages of 35 and 50, though it can occur in older adults and children.1 Scientists estimate that less than 10% of all asthma cases are a severe type like EA.2 Males and females are equally affected.1
What causes eosinophilic asthma?
Doctors do not know why some people get eosinophilic asthma. They do know that people with EA generally do not have allergies to dust mites, pollen, smoke or pet dander like people with more common types of asthma.1
How is eosinophilic asthma diagnosed?
Eosinophilic asthma is diagnosed when a doctor finds elevated numbers of eosinophils in a blood or sputum sample.1,2 Less often, your doctor will perform a bronchial biopsy and count the number of eosinophils in a tissue sample taken from the lungs.
A newer test identifies inflammatory biomarkers for eosinophils in the blood, which gives doctors a more accurate idea of whether the person has EA and which medicines are more likely to control their severe eosinophilic asthma.
Other things your doctor may consider when diagnosing eosinophilic asthma are:
- Medical history and physical examination
- Age of onset
- Results of allergy tests
- Lung function tests
- Response to medications tried in the past
EA is sometimes misdiagnosed as chronic obstructive pulmonary disease (COPD).1
How can it be treated?
Eosinophilic asthma is usually treated with a combination of corticosteroids (both inhaled and oral), long-acting bronchodilators and a biologic treatment such as mepolizumab (Nucala), reslizumab (Cinqair), or benralizumab (Fasenra).1
Mepolizumab, reslizumab, and benralizumab are anti-IL-5 agents, or interleukin-5 antagonist monoclonal antibodies. These medicines are thought to reduce the level eosinophils in the blood. These medicines block IL-5 signaling, which reduces the production and survival of eosinophils, which relieves EA symptoms.4
Dupilumab (Dupixent), a drug for moderate-to-severe asthma may also be prescribed for EA. It does not work on eosinophils. This medicine inhibits the overactive signaling of interleukin-4 (IL-4) and interleukin-13 (IL-13), two key proteins that contribute to the inflammation that may cause moderate-to-severe asthma. This effect demonstrates a reduction of inflammatory biomarkers, including fractional exhaled nitric oxide (FeNO), immunoglobulin E (IgE) and eotaxin-3 (CCL26).5,6
Omalizumab (Xolair), which tends to work for people with allergic asthma, does not usually improve symptoms of EA. Lebrikizumab and tralokinumab are two drugs that are being studied for use in people with uncontrolled, severe asthma.1