Acute Eosinophilic Pneumonia

National Organization for Rare Disorders, Inc.

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It is possible that the main title of the report Acute Eosinophilic Pneumonia is not the name you expected. Please check the synonyms listing to find the alternate name(s) and disorder subdivision(s) covered by this report.


  • AEP
  • IAEP
  • idiopathic acute eosinophilic pneumonia

Disorder Subdivisions

  • None

General Discussion


Acute eosinophilic pneumonia (AEP) is a rare disorder characterized by the rapid accumulation of eosinophils in the lungs (pulmonary eosinophilia). Eosinophils are a type of white blood cell and are part of the immune system. They are usually produced in response to allergens, inflammation or infection (especially parasitic ones) and are particularly active in the respiratory tract. Common symptoms associated with AEP include progressive shortness of breath (dyspnea) of rapid onset, cough, fatigue, night sweats, low grade fevers, and unintended weight loss. AEP can rapidly progress to cause acute respiratory failure. The exact cause of the disorder is unknown (idiopathic) in many cases.


AEP was first described as a distinct entity in the medical literature in 1989. AEP is classified as a form of eosinophilic lung disease, a large group of interstitial lung diseases. AEP is different from chronic eosinophilic pneumonia (CEP), which is marked by slower progression, lack of progression to acute respiratory failure, frequent relapses and is often associated with asthma. For more information on CEP, choose "chronic eosinophilic pneumonia" as your search term in the NORD Rare Disease Database.


AEP is characterized by a sudden, rapid onset of symptoms usually within 1-7 days. However, in some cases, symptoms may develop less rapidly over the course of up to one month. AEP often develops in young, otherwise healthy individuals. Associated symptoms are nonspecific and can include fevers, cough, difficulty breathing (dyspnea) and chest pain. Less common symptoms include fatigue, muscle pain (myalgia), joint aches, and abdominal discomfort or pain.

AEP can rapidly progress to acute respiratory failure. Acute respiratory failure occurs when the level of oxygen in the blood decreases severely (hypoxemia), potentially resulting in life-threatening breathing complications. This can occur within a few days or even within hours in individuals with AEP. Approximately two-thirds of individuals may require mechanical ventilation.

AEP is an extremely rare disorder and may be confused with infectious pneumonia, which prevents physicians from developing a definitive picture of associated symptoms and prognosis. As AEP becomes better known and more affected individuals are identified, researchers should be able to obtain a better clinical understanding of the disorder. For example, some researchers believe that milder cases of AEP exist, but may go undiagnosed. These mild cases may cause less severe symptoms and complications.


The cause of AEP is unknown (idiopathic). Researchers believe that AEP develops due to an unidentified, nonspecific triggering agent that causes the body to produce eosinophils. The exact reason for the overproduction and accumulation of eosinophils is unknown.

Several environmental factors including occupational factors have been linked to the development of AEP including exposure to dust and smoke. It is unlikely that a single environmental factor causes AEP. Most likely, multiple factors are necessary for the development of the disorder. The triggering factor in AEP can be different from one individual to another.

In many cases, cigarette smoking is believed to play a role in the development of the disorder, specifically in individuals who had just begun smoking within the last three months before the onset of the disorder, have resumed smoking after temporary cessation, or have recently increased the number of cigarettes smoked daily. Several reports in the medical literature have demonstrated an association between cigarette smoking and AEP in a subset of affected individuals. The exact role that smoking plays in the development of AEP in such cases is not fully understood.

Occupational factors that have been linked to the development of AEP are numerous and varied. These cases suggest that breathing in some type of contaminate or inhaled agent that induces damage to the lungs can trigger AEP.

Additional reports in the medical literature have linked some cases of AEP to the use of specific drugs. Drug-induced cases have been linked to daptomycin, an antibiotic, and velafaxine, an antidepressant.

Some researchers believe that cytokines (specialized proteins secreted from certain immune system cells that either stimulate or inhibit the function of other immune system cells) may play a role in the development of eosinophilic disorders. Interleukin-5 (IL-5) is a cytokine that is known to be a regulator of the development and function of eosinophils. It is possible that IL-5 might suppress the normal disintegration (apoptosis) of eosinophils resulting in their accumulation within the lungs and bloodstream. More research is necessary to determine the exact role, if any, of IL-5 in the development of eosinophilic disorders such as AEP.

Affected Populations

AEP affects males approximately twice as often as females. Fewer than 100 cases have been reported in the medical literature and the exact prevalence is unknown. AEP can affect individuals of any age, but occurs most often in individuals between 20-40 years of age.

Standard Therapies


A diagnosis of AEP is based upon identification of characteristic symptoms, a detailed patient history, a thorough clinical evaluation, and a variety of specialized tests especially bronchoalveolar lavage (BAL). The presence of other causes of pulmonary eosinophilia such as parasitic infections or exposure to certain drugs must be systematically investigated.

Clinical Testing and Work-Up

An exam known as BAL, may be used in the diagnosis of AEP. During a BAL, a narrow tube (flexible bronchoscope) is slid down the windpipe into the lungs and a sterile solution is passed through the tube washing out (lavaging) cells. This fluid is collected and then the tube is removed, allowing the cells to be studied. BAL fluid in individuals with AEP reveals abnormally high levels of eosinophils (greater than 25%).

Specific imaging techniques may be used to help confirm a diagnosis of AEP including chest x-ray, however abnormalities are not specific. Chest x-rays in individuals with AEP generally show white lines or hazy patches (infiltrates) in the lungs.

During the acute phase, pulmonary function tests show a restricted or obstructed pattern.


Individuals with AEP respond rapidly to high doses of corticosteroids for a few weeks. In most cases, there is usually no relapse after steroid therapy is stopped and the prognosis is excellent. Corticosteroid therapy is initiated only after an infectious cause of pulmonary eosinophilia has been ruled out. Within the medical literature, the dose and duration of corticosteroid therapy has varied greatly. Consequently, there is no agreed upon dose or duration for corticosteroid therapy in individuals with AEP. Individuals reported in the medical literature received intravenous corticosteroids initially, followed by oral administration afterward.

Because the disorder often progresses rapidly, many individual require admission into an intensive care unit to receive respiratory support. Respiratory support can consist of either invasive or noninvasive mechanical ventilation. Invasive ventilation provides respiratory support along with an artificial airway, such as one created via a tracheostomy. With a tracheostomy, a tube is surgically implanted into the windpipe (trachea) to maintain an airway. Noninvasive ventilation provides respiratory support via a ventilator without the creation of an artificial airway. Noninvasive ventilation has led to rapid improvement and weaning is often possible in under a week.

In some cases, AEP improves without any treatment (spontaneous remission).

Investigational Therapies

Information on current clinical trials is posted on the Internet at All studies receiving U.S. government funding, and some supported by private industry, are posted on this government web site.

For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:

Toll-free: (800) 411-1222

TTY: (866) 411-1010


For information about clinical trials sponsored by private sources, in the main, contact:



Cordier JF, Cottin V. Eosinophilic Pneumonias. In: Interstitial Lung Disease, 5th ed. Schwarz MI, King Jr. TE, eds. 2011, People's Medical Publishing House, Shelton, CT. pp. 833-893

Cottin V. Idiopathic eosinophilic pneumonias. In: European Respiratory Monograph: Clinical Handbooks for the Respiratory Professional. Orphan Lung Diseases. Cordier JF, ed. 2011, European Respiratory Society, United Kingdom. Pp. 118-139.


Tsigkaropoulou E, Hatzilia D, Rizos E, et al. Venlafaxine-induced acute eosinophilic pneumonia. Gen Hosp Psychiatry. 2011;33:e7-9.

Miller BA, Gray A, Leblanc TW, et al. Acute eosinophilic pneumonia secondary to daptomycin: a report of three cases. Clin Infect Dis. 2010;50:63-68.

Jeong YJ, Kim KL, Seo IJ, et al. Eosinophilic lung diseases: a clinical, radiologic, and pathologic overview. Radiographics. 2007;27:617-637.

Shorr AF, Scoville SL, Cersovsky SB, et al. Acute eosinophilic pneumonia among US military personnel deployed in or near Iraq. JAMA. 2004;292:2997-3005.

Allen JN, Magro CM, King MA. The eosinophilic pneumonias. Semin Respir Crit Care Med. 2002;23:127-134.

Poletti V, Costabel U, Casoni GL, et al. Rare infiltrative lung diseases: a challenge for clinicians. Respiration. 2004;71:431-443.

Philit F, Etienne-Mastroianni B, Parrot A, et al. Idiopathic acute eosinophilic pneumonia. A study of 22 patients. Am J Respir Crit Car Med. 2002;166:1235-1239.


Saukkonen JJ. Pulmonary Eosinophilia. Emedicine Journal, June 14 2006. Available at: Accessed on: December 19, 2011.

Philit F, Cordier JF. Idiopathic acute eosinophilic pneumonia. Orphanet encyclopedia, February 2002. Available at: Accessed on: 12/19/2011.


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Genetic and Rare Diseases (GARD) Information Center

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Campaign Urging Research for Eosinophilic Disease (CURED)

PO Box 32

Lincolnshire, IL 60069

Tel: (847)361-3292



Cincinnati Center for Eosinophilic Disorders

Cincinnati Children's Hospital Medical Center

3333 Burnet Avenue

MLC 2010

Cincinnati, OH 45229-3039

Tel: (513)636-2233

Fax: (513)636-9069

Tel: (800)344-2462

TDD: (513)636-4900



American Partnership for Eosinophilic Disorders

PO Box 29545

Atlanta, GA 30359

Tel: (713)493-7749

Fax: (713)493-7749


For a Complete Report

This is an abstract of a report from the National Organization for Rare Disorders, Inc.® (NORD). Cigna members can access the complete report by logging into For non-Cigna members, a copy of the complete report can be obtained for a small fee by visiting the NORD website. The complete report contains additional information including symptoms, causes, affected population, related disorders, standard and investigational treatments (if available), and references from medical literature. For a full-text version of this topic, see