What is Eosinophilic Pneumonia?
Eosinophilic pneumonia is a term for various lung conditions that show an excessive amount (defined as more than 500 per liter) of a type of white blood cell called eosinophils in the blood or lung fluid. Sometimes, these cells have even invaded the lung tissue itself – this can be seen on a lung biopsy. Eosinophilic lung diseases are grouped into ‘Primary’ or ‘Secondary’, depending on whether an underlying cause can be identified or not.
When we say ‘eosinophilic pneumonia’, we’re mainly talking about a primary disease involving eosinophils. This can be broken down further into acute eosinophilic pneumonia and chronic eosinophilic pneumonia.
Acute eosinophilic pneumonia is a sudden feverish illness, which can be spotted on medical imaging due to widespread infiltration in the lungs, and may even cause sudden, severe breathing problems.
What Causes Eosinophilic Pneumonia?
Sometimes, the number of a certain type of white blood cell, called eosinophils, can increase in the lung tissue. This can be due to either infections or non-infections.
Non-infection related causes can include:
* Unknown reasons (idiopathic)
* Certain medications like ampicillin, nitrofurantoin, ranitidine, acetaminophen, and iodides
* Exposure to toxins
* Environmental triggers
* Cancer
* Breathing problems due to allergies (allergic bronchopulmonary aspergillosis)
* Conditions that result in a high number of eosinophils (hypereosinophilic syndromes)
* A rare disease that involves inflammation of the blood vessels (Churg-Strauss syndrome)
* Smoking
Infections that can cause this type of white blood cell to increase are usually due to parasites. These parasites can include ascariasis, Strongyloides (a type of roundworm), hookworms, filarial nematodes (a type of parasitic worm), Paragonimus (a type of lung fluke), and Toxocara (a type of roundworm).
Cases of acutely eosinophilic pneumonia, which is a sudden and severe inflammation of the lungs, are mostly due to unknown causes. They can also be caused by parasitic infections and exposure to certain drugs or toxins.
Risk Factors and Frequency for Eosinophilic Pneumonia
Idiopathic acute eosinophilic pneumonia is a condition that can happen to anyone, but it’s often seen in males between the ages of 20 to 40. People with chronic myelogenous leukemia, HIV, and smokers are also prone to this condition.
- Chronic eosinophilic pneumonia is most common in white women.
- The age group with the highest number of cases is between 30 to 40 years.
- About half of these patients also have asthma.
Signs and Symptoms of Eosinophilic Pneumonia
Acute eosinophilic pneumonia is a rapid lung condition where symptoms develop within two weeks. This illness often presents with a number of symptoms such as a cough, fever, difficulty breathing and night sweats. Furthermore, muscle aches, chest pain and severe difficulty breathing can also occur, sometimes resulting in respiratory failure. People with this condition can present symptoms similar to acute lung injury or severe respiratory distress without any preceding illness. However, lack of organ failure elsewhere in the body and absence of shock sets it apart. Examination of such patients might reveal widespread crackling sounds when listening to the lungs.
On the other hand, chronic eosinophilic pneumonia is a more gradual and slow-progressing lung condition. Symptoms are usually present for several months before a formal diagnosis is made. In addition to the common symptoms, affected individuals may also experience moderate weight loss. Over time, their difficulty breathing tends to worsen and may be paired with wheezing sounds, particularly in adult patients who also have asthma.
Below is a list of common symptoms:
- Cough
- Fever
- Difficulty breathing
- Night sweats
For Acute eosinophilic pneumonia, these additional symptoms may be present:
- Muscle aches
- Chest pain
- Severe difficulty breathing, sometimes leading to respiratory failure
- Widespread crackling sounds in lungs (as heard during examination)
For Chronic eosinophilic pneumonia, these additional symptoms might occur:
- Progressing difficulty in breathing
- Wheezing sounds, especially in adults with asthma
- Moderate weight loss
Testing for Eosinophilic Pneumonia
Idiopathic Acute Eosinophilic Pneumonia usually requires ruling out other conditions before being diagnosed. Several tests and examinations are needed, including:
– A bronchoalveolar lavage (BAL), a procedure where a tube is inserted into your airways to collect a sample of your lung cells.
– A blood test, which might reveal leukocytosis, a condition where there are too many white blood cells. However, eosinophils, a type of white blood cell, are not usually found to be abundant at first.
– Tests for Immunoglobulin E (IgE), a type of protein that is involved in allergic reactions. Moderate elevations may be found.
– Pulmonary function tests, which are tests that measure how well your lungs work, may reveal a restrictive ventilatory defect (limited ability to fill the lungs with air) and reduced DLCO (ability of lungs to transfer gas from inhaled air to the red blood cells in blood vessels).
– Chest X-rays: At first, these may not show anything specific but as the disease progresses, widespread hazy areas may appear.
– Presence of pleural effusion (excess fluid around the lungs) is common.
– A CT scan can also confirm the diagnosis, but usually it is not required.
– Analysis of fluid, which can show a high pH level and an abundance of eosinophils.
As for Chronic Eosinophilic Pneumonia, diagnosis depends on the symptoms, chest imaging, and results of the BAL and is made after ruling out lung or systemic infections. The conditions and test results may involve:
– An abundance of eosinophils in the BAL, usually accounting for over 40 percent of white blood cells.
– Moderate leukocytosis with an abundance of eosinophils in the blood for most patients.
– Half of the patients may have elevated IgE levels.
– The presence of normocytic, normochromic anemia (a condition where you don’t have enough healthy red blood cells), and thrombocytosis (high platelet count).
– Elevated ESR (erythrocyte sedimentation rate, a blood test that can reveal inflammatory activity in your body).
– Pulmonary function tests that depend on the severity of the disease; lung function can appear restricted, obstructed, or normal.
– Chest x-rays showing infiltrates (accumulation of cells or fluids) which are typically seen in the middle or upper areas of both lungs.
Treatment Options for Eosinophilic Pneumonia
If you have an acute case of eosinophilic pneumonia, a condition where a specific type of white blood cell called eosinophils build up in your lungs and cause inflammation, you will initially receive supportive treatment. This includes supplemental oxygen and a class of medications known as glucocorticoids to help quickly reduce inflammation.
While waiting for your doctor to determine the exact cause of the pneumonia, you may be put on mechanical ventilation to help with your breathing. They may also start you on a broad classification of antibiotics as a preventative measure, even before the exact bacteria causing the infection are identified.
Glucocorticoids, a type of steroid hormone, are recommended for everyone with acute eosinophilic pneumonia. These are usually delivered intravenously (through a needle into a vein) or taken orally (by mouth). They can cause rapid improvement in symptoms within one to two days. Without glucocorticoids therapy, the condition can trigger progressive lung disease leading to respiratory failure. Once you are breathing properly again, your doctor might suggest continuing with an oral form of glucocorticoids for up to a month. After that, they will reduce the dosage gradually over several weeks.
In many cases, glucocorticoids cause an impressive and rapid response. Symptoms often improve within an hour, and lung X-rays show complete resolution of the infection within a month.
When eosinophilic pneumonia is chronic, meaning it lasts for a long time or keeps returning, the standard treatment involves more extended use of glucocorticoids. After your symptoms and X-ray results have returned to normal, your doctor might recommend ongoing treatment with a glucocorticoid called prednisone. This treatment might last at least three months and optimally 6 to 9 months. Some patients may require even longer treatment. Afterwards, your doctor may transition you to inhaled corticosteroids, allowing you to stop taking oral steroids.
What else can Eosinophilic Pneumonia be?
When assessing your lung health, doctors may need to consider a range of possible conditions that could be affecting you. These might include:
- Asthma or allergies
- Broncho-centric granulomatosis, a rare type of lung disease
- Bronchiolitis obliterans organizing pneumonia, a condition that causes inflammation and blockage of the smallest airways in your lungs
- Certain types of infections, such as fungal infections caused by Coccidioides, Aspergillus, or Pneumocystis jirovecii
- Interstitial lung diseases, which are a group of conditions that cause scarring of lung tissue
- Malignancy, which could indicate a type of lung cancer
What to expect with Eosinophilic Pneumonia
As soon as the diagnosis of acute eosinophilic pneumonia, a lung disease, is confirmed and treatment with drugs called corticosteroids is begun, the outlook is generally excellent, thanks to a strong response to the treatment.
In some cases, a longer course of therapy with a type of steroid medication, known as glucocorticoids, might be needed if there’s a risk of the condition coming back. However, even for patients dealing with chronic (long-term) eosinophilic pneumonia, the overall outlook is still good.