Bronchiolitis obliterans organising pneumonia

An inflammatory disorder involving both the peripheral bronchioles and alveoli simultaneously. It has distinctive radiographic findings, histological features, and response to corticosteroids (unlike usual interstitial pneumonia).

Most common type is idiopathic BOOP; other types include focal nodular, post-infection, drug-related, rheumatological, immunological, organ transplantation, radiotherapy, 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 computed tomography 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 organising pneumonia (BOOP) is defined as organised polypoid granulation tissue in the distal airways extending into the alveolar ducts and alveoli.[1]Epler GR, Colby TV. The spectrum of bronchiolitis obliterans. Chest. 1983;83:161-162. http://www.sciencedirect.com/science/article/pii/S0012369215399633 http://www.ncbi.nlm.nih.gov/pubmed/6822090?tool=bestpractice.com [2]Epler GR, Colby TV, McLoud TC, et al. Bronchiolitis obliterans organizing pneumonia. N Engl J Med. 1985;312:152-158. http://www.ncbi.nlm.nih.gov/pubmed/3965933?tool=bestpractice.com [3]Epler GR. Bronchiolitis obliterans organizing pneumonia, 25 years: a variety of causes, but what are the treatment options? Expert Rev Respir Med. 2011;5:353-361. http://www.ncbi.nlm.nih.gov/pubmed/21702658?tool=bestpractice.com BOOP is an inflammatory disorder involving both the peripheral bronchioles and alveoli simultaneously and has distinctive radiographic findings, histological features, and response to therapy.[Figure caption and citation for the preceding image starts]: Medium-powered pathology slide showing circular and branching bronchioles filled with polypoid plugs of granulation tissue and alveoli filled with organising pneumoniaFrom the collection of Gary R. Epler, MD [Citation ends].

The term cryptogenic organising pneumonia (COP) is a general term referring to organised inflammatory process in the alveoli from an unknown cause.[4]Travis WD, Costabel U, Hansell DM, et al. An official American Thoracic Society/European Respiratory Society statement: Update of the international multidisciplinary classification of the idiopathic interstitial pneumonias. Am J Respir Crit Care Med. 2013 Sep 15;188(6):733-48. https://www.atsjournals.org/doi/full/10.1164/rccm.201308-1483ST http://www.ncbi.nlm.nih.gov/pubmed/24032382?tool=bestpractice.com COP is sometimes noted as a preferred term because it captures an 'acinar' rather than an airway disease, and BOOP may be confused with obliterative bronchiolitis.[5]Bradley B, Branley HM, Egan JJ, et al; British Thoracic Society Interstitial Lung Disease Guideline Group, British Thoracic Society Standards of Care Committee; Thoracic Society of Australia; New Zealand Thoracic Society; Irish Thoracic Society. Interstitial lung disease guideline. Thorax. 2008;63(suppl 5):v1-v58. http://thorax.bmj.com/content/63/Suppl_5/v1.full http://www.ncbi.nlm.nih.gov/pubmed/18757459?tool=bestpractice.com

However, the author uses the term BOOP because it continues to be recognised and used throughout the world. It is a specific pulmonary lesion recognised 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 computed tomography 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 non-idiopathic types such as post-infection BOOP; drug-related BOOP; connective tissue and immunological 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.