What Is Eosinophilic Pneumonia?

What Is Eosinophilic Pneumonia?

Eosinophilic pneumonia is a rare type of lung disease. What makes eosinophilic pneumonia different from regular pneumonia is the increased number of eosinophils (a type of white blood cell) in the lungs. These white blood cells are part of the immune system. Unlike other parts of the immune system, eosinophils usually respond to allergens, and when they accumulate in high numbers in the lungs, they cause inflammation. When both the lung airways and lung airsacs (alveoli) become inflamed due to eosinophils, low oxygen levels in the bloodstream can occur.

Causes

Because eosinophilic pneumonia involves a reaction from the immune system (in the form of white blood cells called eosinophils), it can have a variety of causes. These causes can include:

• Allergies
• Autoimmune disease
• Cancer
• Inhaled toxins, particulate metals or dust
• Medications
• Parasites
• Smoking

In some cases, it may be hard to determine the exact cause of eosinophilic pneumonia. These cases are called “idiopathic,” which means the cause is unknown.  

Types

Acute Eosinophilic Pneumonia

Acute eosinophilic pneumonia is characterized by a more sudden onset and faster progression. It can lead to respiratory failure and require hospitalization. Acute eosinophilic pneumonia results from the excessive activation of type-2 immune cells and the production of type-2 cytokines such as interleukin-5. This results in an excessive influx of eosinophils in the lung. 

Chronic Eosinophilic Pneumonia

Chronic eosinophilic pneumonia typically has a slower onset of symptoms, taking from weeks to months. This condition can occur with blood cancer, autoimmune disease, fungal infection or parasitic infection. Even if the exact cause is unknown, the underlying immune activation is the same as in the acute form. High levels of type-2 immune cells and the production of type-2 cytokines such as interleukin-5 result in excessive eosinophils in the lung. 

Signs and Symptoms

Different types of eosinophilic pneumonia and underlying causes may produce different symptoms. The most common symptoms include:

• Bloody mucus
• Chest tightness
• Coughing
• Fever
• Muscle aches
• Rapid breathing
• Shortness of breath
• Wheezing

Symptoms of acute eosinophilic pneumonia are more severe and can lead to hospitalization or even respiratory failure. The symptoms of chronic eosinophilic pneumonia can be similar to acute eosinophilic pneumonia but do not progress as quickly and are less severe than the acute type. People with chronic eosinophilic pneumonia may have a lingering illness and generally feel unwell.

If you have symptoms of eosinophilic pneumonia, it’s important to contact your doctor immediately. In severe cases, eosinophilic pneumonia can result in hospitalization or even respiratory failure.

Diagnosis

When examining you for eosinophilic pneumonia, your doctor will consider your family history and potential contributing environmental factors. The following tests may be administered to help determine your diagnosis.

Imaging Tests

CT scan of the chest: A CT or CAT scan is a shortened name for computerized tomography. During a CT scan of the chest, detailed pictures are taken of cross sections or slices of the thoracic structures in your body. Thoracic structures include your lungs, heart and the bones around these areas. Sometimes intravenous contrast is administered to better see the blood vessels in the lung.

X-rays: X-rays can show irregularities or damage in the lungs caused by eosinophilic pneumonia. You doctor may verify a diagnosis or evaluate what other diseases or conditions may be present with other tests.

Lab Tests

Blood tests: Blood tests can determine the level of eosinophils circulating in the blood. Other blood tests may check for other markers of inflammation or underlying disease in the blood. 

Procedures

Biopsy: In order to determine if a pneumonia fits in the category of eosinophilic pneumonia, a biopsy may be done. This will help confirm that there is an increase in eosinophils in the lung tissue.

Treatment

It's crucial to seek treatment for eosinophilic pneumonia, as the levels of oxygen in your blood can become dangerously low in some cases. This can lead to acute respiratory failure. Treatment of acute eosinophilic pneumonia may require hospitalization in severe cases. Finding and treating underlying causes such as malignancy (cancerous cells that can spread throughout the body), autoimmune disease and infection are important.

Medications

Treatment with intravenous (IV) steroids or other medications that suppress the immune system may be necessary. This may help stop or decrease the inflammation and prevent respiratory failure. Biologic medications targeting interleukin-5 (mepolizumab, reslizumab) or interleukin-5 receptors on eosinophils (benralizumab) are very effective in treating eosinophilic inflammation. These injectable biologics can be used to treat eosinophilic pneumonia.  

In severe cases, when respiratory failure is a concern, it may be necessary to support the patient using a breathing machine while doctors work to pinpoint the cause of the eosinophilic pneumonia.

Clinical Trials

Clinical trials help determine new treatment options for diseases and conditions. Patients with eosinophilic pneumonia have access to clinical trials and should speak with their physician to determine what trials might work best for them.