An inflammatory disorder involving both the peripheral bronchioles and alveoli simultaneously. It has distinctive radiographic findings, histologic features, and response to corticosteroids (unlike usual interstitial pneumonia).
Most common type is idiopathic BOOP; other types include focal nodular, postinfection, drug-related, rheumatologic, immunologic, organ transplantation, radiation therapy, environmental, and miscellaneous BOOP.
Accounts for 20% to 30% of all cases of chronic infiltrative lung diseases. It occurs equally among men and women, and is not related to smoking.
High-resolution chest CT scan shows bilateral patchy triangular ground-glass opacities with air bronchograms usually located peripherally.
Lung biopsy may be required to establish the definitive diagnosis in patients with unusual findings or severe disease.
Idiopathic BOOP is treated with corticosteroids.
Cases with an underlying cause (e.g., drug-related BOOP) should have the causative factor removed; corticosteroid therapy is indicated in some cases.
Bronchiolitis obliterans organizing pneumonia (BOOP) is defined as organized polypoid granulation tissue in the distal airways extending into the alveolar ducts and alveoli.    BOOP is an inflammatory disorder involving both the peripheral bronchioles and alveoli simultaneously and has distinctive radiographic findings, histologic features, and response to therapy.
The term cryptogenic organizing pneumonia (COP) is a general term referring to organized inflammatory process in the alveoli from an unknown cause.   The British Thoracic Society guideline for interstitial lung disease contains the term COP, which is noted as a preferred term because it captures an "acinar" rather than an airway disease, and BOOP may be confused with obliterative bronchiolitis. 
However, the author uses the term BOOP because it continues to be recognized and used throughout the world. It is a specific pulmonary lesion recognized by pathologists with a characteristic clinical pattern and response to treatment. BOOP is simultaneous inflammation of the distal bronchiolar airways, respiratory bronchioles, alveolar ducts, and alveoli. BOOP is a diffuse interstitial parenchymal disease and acinar disease and not an airway disease, especially because of the presence of crackles, decreased diffusing capacity, no airflow obstruction, and high-resolution chest CT scans showing triangular-shaped, ground-glass opacities with air bronchograms.
BOOP is not confused with obliterative bronchiolitis because BOOP is a diffuse parenchymal lung disease and not an airway disease; wheezing is not a common symptom of BOOP; crackles, and not wheezes, are heard by auscultation in BOOP; the FEV1/FVC ratio is normal or slightly increased in BOOP, not decreased as in airway obstructive diseases; and the radiographic findings show bilateral patchy infiltrates, not normal or hyperinflation seen in airflow obstructive diseases.
The term BOOP is also used for nonidiopathic types such as postinfection BOOP; drug-related BOOP; connective tissue and immunologic disease-related BOOP; bone marrow, stem cell, and lung transplant-related BOOP; radiation therapy-related BOOP; occupational and environmentally related BOOP; and continually newly described systemic disease-related BOOP.
Finally, the term BOOP is easy for patients to remember and use to advance their understanding of the disease process by obtaining accessible scientific publications.
Clinical Associate Professor
Harvard Medical School
GRE is an author of several references cited in this monograph.
Professor of Medicine and Director
Division of Pulmonary/Critical Care/Allergy/Sleep Medicine
Medical University of South Carolina
SS declares that he has no competing interests.
National Jewish Medical and Research Center
TLC has been reimbursed by the American College of Chest Physicians (ACCP), American Academy of Sleep Medicine, American Thoracic Society, and Cephalon, the manufacturer of modafinil, for attending several conferences. He has been paid by the ACCP for running educational programs and by Elsevier for serving as consultant of the Sleep Medicine Clinics. He has also received research funding from the National Institutes of Health, Respironics, Restore, and Schwarz Pharma, and has been a member of the speakers' bureau for GlaxoSmithKline.
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