Eosinophilic Pneumonia - Causes, Symptoms, Diagnosis, and Treatment

Introduction

Eosinophilic pneumonia is a rare disease caused by eosinophilic infiltration in the lung parenchyma. It is characterized by a group of disorders that includes a wide range of lung conditions that are caused by infectious or noninfectious factors. It affects people of any age predisposed to factors like smoking, allergic reaction, and parasitic roundworm disease.

What Does Eosinophil Mean?

Eosinophils are one type of white blood cell that plays a role in the immune system. They are produced in the bone marrow. They constitute 1 % to 5 % of white blood cells in healthy individuals. Conditions like allergies, asthma, infections, cancer, or certain medications can increase the eosinophil count (eosinophilia). Eosinophils release enzymes and proteins to destroy abnormal cells. An abnormal increase in the eosinophil count can cause inflammation in the tissues and organs.

What Is Eosinophilic Pneumonia?

Eosinophilic pneumonia is a disease caused by the accumulation of eosinophilic infiltrates in the lung parenchyma. It is characterized by a group of infections that affect the lungs. The white blood cells build up in the lungs and blood and cause inflammation. It disrupts the alveoli in the lungs. It can cause respiratory failure if proper treatment is not given. It can be acute or chronic. It is a noncontagious disease.

Is Eosinophilic Pneumonia and Pneumonia the Same?

Bacterial, fungal, or viral infections cause pneumonia. Eosinophilic pneumonia is caused by the accumulation of eosinophils in the lungs. Both conditions are different. However, both conditions can worsen if mucus blocks the airway.

How Is Eosinophilic Pneumonia Classified?

Eosinophilic pneumonia is classified based on its causes, including medications, environmental triggers, parasitic infections, and cancer. It can also occur if the immune system attacks the lungs. If the cause is unknown, it is called idiopathic eosinophilic pneumonia. Eosinophilic pneumonia is classified into the following:

• Acute Eosinophilic Pneumonia - It commonly affects men. It worsens quickly when the blood oxygen level falls and causes respiratory failure.

• Chronic Eosinophilic Pneumonia - It is common in women. It worsens slowly over days or weeks and results in severe symptoms.

• Simple Eosinophilic Pneumonia - It is also called Loffler syndrome. It is caused by a parasitic infection and causes mild or no symptoms.

• Tropical Eosinophilic Pneumonia - It occurs as a hypersensitivity reaction to (microfilaria) Wuchereria bancrofti and Brugia malayi. It can also be caused by helminthic or parasitic infections.

What Are the Causes of Eosinophilic Pneumonia?

Eosinophilic pneumonia can be caused by infectious and noninfectious causes.

The infectious causes include:

• Coccidiomycosis, candida, and aspergillus fungi.

• Human immunodeficiency virus (HIV).

• Trichosporon Terrestre.

• Bacillus Calmette-Guerin (BCG).

• Toxocariasis.

• Parasites like cutaneous larva migrans.

• Ascariasis.

• Strongyloidiasis.

The noninfectious causes include:

• Allergic reactions.

• Inhaled toxins like chemical fumes, particulate metals, or dust.

• Medications like antibiotics, non-steroidal anti-inflammatory drugs, or selective serotonin reuptake inhibitors.

• Underlying conditions like cancer, autoimmune diseases, or inflammatory disease.

• Smoking.

It can also occur in people with COVID-19 (coronavirus disease).

What Are the Symptoms Associated With Eosinophilic Pneumonia?

The symptoms commonly associated with eosinophilic pneumonia are:

• Cough.

• Fever.

• Shortness of breath.

• Night sweats.

Symptoms associated with acute eosinophilic pneumonia are:

• Chest pain.

• Chills.

• Fatigue.

• Muscle ache.

Symptoms associated with chronic eosinophilic pneumonia are:

• Shortness of breath.

• Night sweats.

• Unexplained weight loss.

• Wheezing.

How Does Eosinophilic Pneumonia Occur?

Eosinophilic pneumonia is caused by activated eosinophils. The activated macrophages release chemical mediators and damage the tissues. It damages the epithelial cells and nerves by toxic granule release. Smooth muscle contraction and inflammatory cell recruitment are caused by leukotriene and platelet-activating factor. Tissue damage and remodeling are seen due to the release of cytokines. Eosinophilic pneumonia can be caused by various causes. Eosinophilic overreaction or dysfunction in the lungs is the common cause of eosinophilic pneumonia. The other factors include:

• Medications and Environmental Exposures - Medications like non-steroidal anti-inflammatory drugs, Nitrofurantoin, Phenytoin, Tryptophan, Daptomycin, Ampicillin, and abusive drugs like heroin and cocaine can trigger an allergic response and cause eosinophilic pneumonia. Chemicals like sulfites, aluminum silicate, and cigarette smoke can trigger eosinophilic pneumonia.

• Parasitic Infections - Parasites cause eosinophilic pneumonia by invading the lungs, living in the lungs as a part of their life cycle, or spreading to the lungs through the bloodstream. To defend against the parasites, the eosinophils migrate to the lungs and cause eosinophilic pneumonia by releasing their contents. Parasites that invade the lungs are Paragonimus lung flukes, Echinococcus tapeworm, and Taenia solium tapeworm. Parasites that inhabit the lungs are Ascaris lumbricoides, Strongyloides stercoralis, and the hookworms Ancylostoma duodenale and Necator americanus. If helminths cause eosinophilic pneumonia, it is called Loffler’s syndrome. The parasites cause eosinophilic pneumonia by transporting their eggs to the lungs through the bloodstream.

• Acute and Chronic Eosinophilic Pneumonia - The cause for both types is not known, and it is believed that the acute form may be caused by an immune response to an environmental agent.

How Is Eosinophilic Pneumonia Diagnosed?

The diagnosis of eosinophilic pneumonia is based on the following tests, which include:

• Complete Blood Count - This test is performed to detect the presence of increased levels of eosinophils.

• Chest X-Ray or Computed Tomography Scan - Radiographic images are taken to identify lung abnormalities.

• Biopsy - It is performed to identify the increase in eosinophils in the lung tissues.

• Bronchoalveolar Lavage - A bronchoscope is used to collect fluid from the lungs to detect the presence of an increase in eosinophilic count.

Pulmonary function tests reveal the presence of reduced diffusion capacity for carbon monoxide. Other laboratory abnormalities associated with eosinophilic pneumonia are increased erythrocyte sedimentation rate, iron deficiency anemia, and increased platelets.

How Is Eosinophilic Pneumonia Treated?

The management of eosinophilic pneumonia involves the following:

• Corticosteroids - It is given to treat acute or chronic eosinophilic pneumonia. Intravenous Methylprednisolone or oral Prednisolone are commonly used to reduce inflammation.

• Supplemental Oxygen is required in severe cases.

• Artificial Ventilation - Non-invasive ventilators like bilevel positive airway pressure machines or breathing tubes can be used to treat breathing difficulty.

Conclusion

Eosinophilic pneumonia is a rare respiratory disorder. It is a treatable disorder, and individuals with eosinophilic pneumonia recover well and have a good prognosis. It is important to consult the physician on experiencing respiratory symptoms. Early diagnosis and prompt treatment offer an excellent prognosis and prevent complications.