(Pulmonary Infiltrates With Eosinophilia Syndrome)
(See also Overview of Interstitial Lung Diseases.)
Eosinophilic pneumonia comprises a group of lung diseases in which eosinophils (a type of white blood cell) appear in increased numbers in the lungs and usually in the bloodstream.
Certain disorders, drugs, chemicals, fungi, and parasites may cause eosinophils to accumulate in the lungs.
People may cough, wheeze, or feel short of breath, and some people develop respiratory failure.
Doctors use x-rays and laboratory tests to detect the disorder and determine the cause, especially if parasites are suspected as the cause.
Corticosteroids are usually given.
Eosinophils participate in the immune response of the lung. The number of eosinophils increases during many inflammatory and allergic reactions, including asthma, which frequently accompanies certain types of eosinophilic pneumonia. Eosinophilic pneumonia differs from typical pneumonias in that there is no suggestion that the tiny air sacs of the lungs (alveoli) are infected by bacteria, viruses, or fungi. However, the alveoli and often the airways do fill with eosinophils. Even the blood vessel walls may be invaded by eosinophils, and the narrowed airways may become plugged with an accumulation of secretions (mucus) if asthma develops.
Löffler syndrome, a form of eosinophilic pneumonia, may cause no symptoms or mild respiratory symptoms (most often dry cough). Chest x-rays and blood tests to find elevated levels of eosinophils in the blood are needed for diagnosis. Löffler syndrome is often part of an infestation by any of several species of nematode worms called filaria; however, a cause may not be identified in as many as one third of people. The disease usually resolves within 1 month. Doctors may give corticosteroids to reduce symptoms and help reduce inflammation.
The exact reason that eosinophils accumulate in the lungs is not well understood, but it may be a type of allergic reaction. Often it is not possible to identify the substance that is causing the allergic reaction. However, there are some known causes of eosinophilic pneumonia, including
Certain drugs (for example, penicillin, aminosalicylic acid, carbamazepine, l-tryptophan, naproxen, isoniazid, nitrofurantoin, phenytoin, chlorpropamide, and sulfonamides [such as trimethoprim/sulfamethoxazole])
Chemical fumes (for example, cocaine or nickel inhaled as a vapor)
Fungi (typically Aspergillus fumigatus)
Parasites (particularly roundworms, including nematodes)
Systemic disorders (for example, eosinophilic granulomatosis with polyangiitis)
Symptoms may be mild or life threatening, and acute or chronic.
Acute eosinophilic pneumonia progresses quickly. It may cause fever, chest pain worsened by deep breathing, shortness of breath, cough, and a general feeling of illness. The level of oxygen in the blood can decrease severely, and acute eosinophilic pneumonia can progress to acute respiratory failure in a few hours or days if not treated.
Löffler syndrome may cause mild respiratory symptoms, if any. A person may cough, wheeze, and feel short of breath but usually recovers quickly.
Chronic eosinophilic pneumonia, which slowly progresses over days or weeks, is a distinct disorder that may also become severe. It tends to remit and recur on its own and may worsen over weeks or months. Life-threatening shortness of breath can develop if the condition is not treated.
When doctors suspect eosinophilic pneumonia, they first do a chest x-ray.
In acute eosinophilic pneumonia, the chest x-ray is abnormal, but similar abnormalities can occur in other conditions.
In chronic eosinophilic pneumonia, chest x-rays are more effective for diagnosis.
Often, computed tomography (CT) of the chest is needed for diagnosis, particularly for acute eosinophilic pneumonia.
The number of eosinophils in the blood are measured. In acute eosinophilic pneumonia, the number of eosinophils in the blood may be normal. In chronic eosinophilic pneumonia, tests show large numbers of eosinophils in the blood, sometimes as many as 10 to 15 times the normal number.
Microscopic examination of cells from washings of the alveoli obtained during bronchoscopy typically shows clumps of eosinophils. Other laboratory tests may be done to search for an infection with fungi or parasites. These tests may include microscopic examination of stool specimens to look for worms and other parasites.
Eosinophilic pneumonia may be mild, and people with the disease may get better without treatment.
For acute eosinophilic pneumonia, a corticosteroid such as prednisone is usually needed.
In chronic eosinophilic pneumonia, prednisone may be needed for many months or even years.
If a person develops wheezing, the same treatments used for asthma are given as well. If worms or other parasites are the cause, the person is treated with appropriate drugs. Ordinarily, drugs that may be causing the illness are stopped.