There are many types of asthma, and eosinophilic asthma is one of the most severe. People with eosinophilic asthma have an excess of inflammatory immune cells known as eosinophils in their blood and lungs, which can cause different symptoms than other types of asthma.
Eosinophilic asthma is often more severe than other types of asthma, in part because the excess of eosinophils causes swelling, inflammation, and mucous production that can clog the airways and make breathing challenging. Without appropriate treatment, individuals with eosinophilic asthma may have frequent and severe asthma attacks. Managing these attacks usually requires inhaled medications and carefully avoiding asthma triggers.
People living with eosinophilic asthma may also experience chronic rhinosinusitis, or recurring sinus issues like loss of smell, a runny nose, facial pressure, and nasal congestion. Nasal polyps, which develop when swollen tissue in the nose blocks airflow, may also be associated with eosinophilic asthma.
Read more about symptoms of eosinophilic asthma.
About 8.4 percent of people in the U.S. have some form of asthma. Eosinophilic asthma is relatively rare, and it’s estimated to account for only 5 percent of adult asthma cases. However, eosinophilic asthma accounts for about half of all severe asthma cases.
Eosinophilic asthma is more common in adult-onset asthma than childhood-onset asthma. Those who develop eosinophilic asthma are usually between the ages of 35 and 50, although it can occur in children and others outside the typical age range. Unlike other forms of asthma, eosinophilic asthma appears to affect men and women equally. People with adult-onset eosinophilic asthma tend to have fewer allergies than people with other kinds of asthma.
Researchers do not know the cause of eosinophilic asthma. Some forms of asthma are triggered by allergens, but that’s not typically the case with eosinophilic asthma.
Eosinophilic asthma is characterized by eosinophils, a type of white blood cell, in the blood and lungs. Eosinophils are specialized immune cells associated with allergic reactions and infections due to parasites or bacteria — and with high levels of inflammation.
Eosinophilic asthma can involve inflammatory cytokines, proteins secreted by cells that can induce inflammation. There is a distinct set of cytokines associated with eosinophilic asthma called T helper 2 (Th2) cytokines. Th2 cytokines include inflammatory molecules known as interleukins (IL) IL-4, IL-5, and IL-13. These cytokines promote the activation of eosinophils and other immune cells, which can then affect the airway.
Eosinophilic inflammation can cause airway damage, which leads to many of the symptoms of asthma. Airway inflammation can have a significant impact on the lungs, including:
All of these changes can affect how well the lungs work.
The diagnostic procedure for eosinophilic asthma may differ from other types of asthma. Most forms of asthma require a lung function test, a physical exam, and sometimes X-rays. While a doctor may still want to perform these tests when diagnosing eosinophilic asthma, they will also have to confirm the presence of high levels of eosinophils in the body (eosinophilia).
To diagnose eosinophilic asthma, a doctor or other health care provider will look for signs of eosinophilia.
A blood test for eosinophil count is the most common way to diagnose eosinophilic asthma. Individuals with 200 to 300 or more eosinophils per microliter of blood may receive a diagnosis of eosinophilic asthma. While a blood test can indicate eosinophilia in the blood, it may not always be a good indication of what is going on in the lungs.
Occasionally, a health care provider may look for eosinophils in the sputum, the mucus coughed out of the lungs. They may order an induced sputum collection. This test involves breathing a saline solution using a nebulizer and then coughing. The health care team will collect any sputum in a specimen cup to analyze it for eosinophils. If the count of eosinophils totals 3 percent or more of the cells in the sample, this may indicate a diagnosis of eosinophilic asthma.
In severe cases, a doctor may want to perform a bronchial biopsy. This approach for diagnosing eosinophilic asthma is more invasive and is less likely to be used for purposes of an initial diagnosis. The procedure is performed under sedation. A scope is then placed into the mouth or nose to gain access to the lungs. A biopsy or sample of tissue will be collected and analyzed for eosinophil content.
Because eosinophilic asthma can impact your quality of life, knowing more about the condition can help you understand the disease and treatment options available. Fortunately, as researchers learn more about how to reduce inflammation during eosinophilic asthma, better treatments are being developed.
Read more about treatment options for eosinophilic asthma.
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