55 Kenosia Avenue
Danbury, CT 06810
Phone: 203.744.0100
Toll Free: 1.800.999.6673

Bronchiolitis Obliterans Organizing Pneumonia

The information in NORD’s Rare Disease Database is for educational purposes only. It should never be used for diagnostic or treatment purposes. If you have questions regarding a medical condition, always seek the advice of your physician or other qualified health professional. NORD’s reports provide a brief overview of rare diseases. For more specific information, we encourage you to contact your personal physician or the agencies listed as “Resources” on this report.

Copyright 2006, 2010, 2013

NORD is very grateful to Gary R. Epler, MD, Pulmonary and Critical Care Medicine, Harvard Medical School, Brigham and Women's Hospital, for assistance in the preparation of this report.

Synonyms of Bronchiolitis Obliterans Organizing Pneumonia

Disorder Subdivisions

General Discussion

Bronchiolitis obliterans organizing pneumonia (BOOP) is a rare inflammatory lung disorder. Symptoms of BOOP include a flu-like illness in many individuals, cough and shortness of breath with exertional activities. Wheezing and hemoptysis are rare. The term bronchiolitis obliterans refers to swirls or plugs of fibrous, granulation tissue filling the small bronchiole airways. Organizing pneumonia refers to organized swirls of inflammatory tissue filling the small spherical units of the lungs referred to as alveoli and the alveolar ducts. Individuals with BOOP experience inflammation of the bronchioles and alveolar lung spherical units simultaneously, which distinguishes it from other similar inflammatory lung disorders.

Although several different known causes of BOOP have been identified, most cases occur for no known reason (idiopathic). Idiopathic BOOP may also be called cryptogenic organizing pneumonia. Some researchers prefer the use of COP to avoid confusion with other lung disorders with similar names. The term cryptogenic denotes that the cause of the disorder is unknown. Others prefer the term BOOP because it the most recognized term for the disorder, and others refer to it as Epler’s pneumonia.


Symptoms of BOOP vary from case-to-case depending upon the specific type. For example, people with idiopathic BOOP have a flu-like illness, while people with BOOP associated with an underlying connective-tissue disorder have cough or shortness of breath. Some individuals with BOOP such as focal BOOP may have no apparent symptoms, while others may have severe respiratory distress as in acute, rapidly-progressive BOOP.

Symptoms usually develop slowly over a few weeks or months. The most common symptom is a persistent, nonproductive cough. Some affected individuals develop a flu-like illness characterized by a sore throat, a general feeling of ill health (malaise), weight loss, and fatigue. Eventually, shortness of breath especially from exertional activities may develop. The shortness of breath and cough may become progressively worse.

Individuals with BOOP may develop small crackling or rattling sounds in the lung (crackles or rales) that are apparent upon physical examination. In rare cases affected individuals may experience chest pain, joint pain (arthralgia), night sweats or coughing up blood (hemoptysis).

A rapidly progressive form of BOOP exists that can progress from symptom onset to acute respiratory failure in only a few days. This form of BOOP may be associated with an underlying fibrotic process.


In most cases, the cause of BOOP is unknown and is referred to as idiopathic BOOP. Causes of BOOP include radiation therapy; exposure to certain fumes or chemicals, post respiratory infections, after organ transplantation; and from more than 35 medications. Systemic disorders associated with BOOP include the connective-tissue diseases, immunological disorders, and inflammatory bowel disease. BOOP has also been seen in association with lung abscess, lung cancer, and lymphoma. Importantly, the BOOP lesion is seen in individuals with idiopathic pulmonary fibrosis, or IPF, and in these situations, the primary lung disease is the IPF and the secondary process is BOOP.

Affected Populations

BOOP affects males and females in equal numbers. It develops in individuals between 40-60 years old, but the disorder may affect individuals of any age. BOOP is estimated to account for 5 to 10% of the chronic infiltrative lung disease in the United States. BOOP has been reported throughout the world. BOOP was first reported in 1985 by Dr. Gary R. Epler.

Related Disorders

Symptoms of the following disorders can be similar to those of BOOP. Comparisons may be useful for a differential diagnosis.

Idiopathic pulmonary fibrosis (IPF) is a fibrosing (scar-producing) and inflammatory lung disorder of unknown origin (idiopathic) characterized by abnormal formation of scar and fibrosis between the spherical, alveolar structures in the lung, which is referred to as the interstitium. These disorders are also called the chronic interstitial pneumonias. Shortness of breath, mild at first, and then severe is the major symptom. Cough sometimes occurs. When severe, the skin may appear slightly bluish (cyanotic) due to lack of circulating oxygen. Complications such as infection or heart problems may develop. The BOOP process is sometimes seen in IPF as the inflammation component. In this situation, the BOOP is secondary to the underlying IPF disorder, and treatment with prednisone may eliminate the BOOP, yet the underlying IPF continues. (For more information on this disorder, choose "idiopathic pulmonary fibrosis" as your search term in the Rare Disease Database.)

Acute interstitial pneumonia (AIP) is an inflammatory lung disorder that progresses rapidly and is distinguished by the particular nature or pattern of cells found on biopsy of the lung. This pattern is almost identical to that found with acute respiratory distress syndrome, or ARDS, and may be confused with it. The name and its abbreviation, AIP, are limited to those cases of unknown cause. (For more information on this disorder, choose "acute interstitial pneumonia" as your search term in the Rare Disease Database.)

Standard Therapies

A diagnosis of BOOP may be made based upon a clinical evaluation, a detailed patient history, identification of characteristic findings, and specialized tests such as x-ray studies, especially a high-resolution chest computed tomography or HRCT , pulmonary function studies that includes a diffusing capacity test, and often a lung biopsy for microscopic tissue analysis The HRCT scan shows "ground glass" densities that are often triangular in shape with the base of the triangle along the chest wall and the airways can often be seen in the ground-glass opacities.

In some cases, the symptoms of BOOP may resolve without treatment especially the post breast radiation-type. In some mild cases such as individuals without symptoms or who have non-progressive disease, the process can be monitored and treated later if necessary. Most individuals with BOOP require treatment with the anti-inflammatory, corticosteroid medication, usually in the form of prednisone. This therapy often results in dramatic improvement with resolution of symptoms within days or weeks. In some situations, the BOOP may recur as the dose is decreased, but the BOOP will respond to an additional course of treatment.

The rapidly progressive form of BOOP is treated with intravenous corticosteroid medication and sometimes with Cytoxan. Individuals with secondary BOOP may improve after treating the underlying condition. Additional treatment is symptomatic and supportive.

Investigational Therapies

For individuals who do not respond to steroid therapy, other agents have been used including cyclophosphamide, erythromycin in the form of azithromycin, and Mycophenolate Mofetil (CellCept). These agents have been beneficial to individuals with BOOP on a case-by-case basis reported in the medical literature (anecdotally). However, research is needed to determine the long-term safety and effectiveness of these potential treatment options for individuals with BOOP.

In rare cases, lung transplantation may be necessary for individuals with BOOP who do not respond to standard treatment options.

Information about clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government website.

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
Email: prpl@cc.nih.gov

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

For information about clinical trials conducted in Europe, contact:

Contact for additional information about bronchiolitis obliterans organizing pneumonia:

Gary R. Epler, MD
Pulmonary and Critical Care Medicine
Brigham and Women's Hospital
Boston, MA

Bronchiolitis Obliterans Organizing Pneumonia Resources



Mason RJ, Broaddus VC, Murray JF, Nadel JA. eds. Murray and Nadel's Textbook of Respiratory Medicine. 4th ed. Elsevier Saunders. Philadelphia, PA; 2005:1297-1300.

Bennett JC, Plum F., eds. Cecil Textbook of Medicine. 20th ed. Philadelphia, PA: W.B. Saunders Co; 1996:394-5.

Fishman AP., ed. Pulmonary Diseases and Disorders, 2nd ed. New York, NY: McGraw-Hill Book Company; 1988: 739-40.

Epler GR. Bronchiolitis obliterans organizing pneumonia, 25 years: a variety of causes, but what are the treatment options? Expert Rev Respir Med. 2011 Jun;5(3):353-361.

Stover DE, Mangino D. Macrolides: a treatment alternative for bronchiolitis obliterans organizing pneumonia? Chest. 2005;128:3611-7.

Oymak FS, Demirbas HM, Mavili E, et al., Bronchiolitis obliterans organizing pneumonia. Clinical and roentgenological features in 26 cases. Respiration. 2005;72:254-62

Lazor R. Cryptogenic organizing pneumonia. Rev Pneumol Clin. 2005;61:193-202.

Husain SJ, Irfan M, Zubairi AS, Salahuddin N. Rapidly-progressing bronchiolitis obliterans organizing pneumonia. Singapore Med J. 2004;45:283.

Al-Saghir AH, Al-Mobeireek AF. Bronchiolitis obliterans organizing pneumonia. Saudi Med J. 2004;25:557-65.

Cordier JF. Cryptogenic organizing pneumonia. Clin Chest Med. 2004;25:727-38.
Cordier JF. Bronchiolitis obliterans organizing pneumonia. Semin Respir Crit Care Med. 2000;21:135-46.

Khan AN. Imaging in Bronchiolitis Obliterans Organizing Pneumonia. eMedicine Journal. Last Update:5/25/2011:10pp. Available at: http://www.emedicine.com/radio/topic117.htm Accessed:1/14/13.

Cordier JF, Costabel U, du Bois RM. Cryptogenic Organizing Pneumonia. Orphanet Encyclopedia. Last Update: October 2004. Available at: http://www.orpha.net/data/patho/GB/uk-CryptOrgPneum.pdf Accessed:1/14/13.

Report last updated: 2013/01/28 00:00:00 GMT+0