Bronchiolitis obliterans

Bronchiolitis obliterans
Bronchiolitis obliterans
Classification and external resources
ICD-9 491.8
DiseasesDB 1704
MeSH D001989

Bronchiolitis obliterans (BO),[1] also called obliterative bronchiolitis (OB)[2] and constrictive bronchiolitis (CB),[3] is a rare and life-threatening form of non-reversible obstructive lung disease in which the bronchioles (small airway branches) are compressed and narrowed by fibrosis (scar tissue) and/or inflammation.[4] Bronchiolitis obliterans is also sometimes used to refer to a particularly severe form of pediatric bronchiolitis caused by adenovirus.

Bronchiolitis means inflammation of the bronchioles and obliterans refers to the fact that the inflammation or fibrosis of the bronchioles partially or completely obliterates the airways.[5]


Signs and symptoms

Bronchiolitis obliterans is a lung disease characterized by fixed airway obstruction. Inflammation and scarring occur in the airways of the lung, resulting in severe shortness of breath and dry cough.

FEV1 (forced expiratory volume in 1 second) should be above 80% of predicted values to be considered normal. Bronchiolitis obliterans reduces this to 16% to 21%.

Symptoms include:

  • dry cough
  • shortness of breath
  • wheezing

The symptoms can start gradually, or severe symptoms can occur suddenly.[3][6]


Bronchiolitis obliterans has many possible causes, including: collagen vascular disease, transplant rejection in organ transplant patients, viral infection (respiratory syncytial virus, adenovirus, HIV, cytomegalovirus), Stevens-Johnson Syndrome, Pneumocystis pneumonia, drug reaction, aspiration and complications of prematurity (bronchopulmonary dysplasia), and exposure to toxic fumes, including: diacetyl, sulfur dioxide, nitrogen dioxide, ammonia, chlorine, thionyl chloride, methyl isocyanate, hydrogen fluoride, hydrogen bromide, hydrogen chloride, hydrogen sulfide, phosgene, polyamide-amine dyes, mustard gas and ozone. It can also be present in patients with rheumatoid arthritis. Certain orally administrated emergency medications, such as activated charcoal, have been known to cause it when aspirated.[citation needed] Additionally, the disorder may be idiopathic (without known cause).[1][2][5]

Industrial inhalants

There are many industrial inhalants that are known to cause various types of bronchiolitis, including bronchiolitis obliterans. [5]

Industrial workers who have presented with bronchiolitis:

  • nylon-flock workers [6]
  • workers who spray prints onto textiles with polyamide-amine dyes [6]
  • battery workers who are exposed to thionyl chloride fumes
  • workers at plants that use or manufacture flavorings, e.g. diacetyl butter-like flavoring [3][6][7]

Diacetyl (Popcorn workers lung)

In rare instances, bronchiolitis obliterans may be caused by inhalation of airborne diacetyl, a chemical used to produce the butter-like flavoring[7] in many foods such as candy, microwave popcorn and wines. This first came to public attention when eight former employees of the Gilster-Mary Lee popcorn plant in Jasper, Missouri, developed bronchiolitis obliterans. In 2000, the Missouri Department of Health called in NIOSH to make a determination of the cause, and to recommend safety measures. After surveying the plant and each patient's medical history, NIOSH recommended respiratory protection for all workers in microwave popcorn production. Due to this event, bronchiolitis obliterans began to be referred to in the popular media as "Popcorn Lung" or "Popcorn Workers Lung".[4][8][9]

One heavy consumer of microwaved popcorn has been diagnosed with this disease, which is the first known case involving a consumer.[13]

On 27 August 2007, Weaver Popcorn Company of Indianapolis promised to replace the diacetyl butter flavor ingredient in Pop Weaver popcorn with another flavoring.[14]

In September 2007, Dr. Cecile Rose, pulmonary specialist at Denver's National Jewish Medical and Research Center, warned federal agencies that consumers, not just flavoring or food factory workers, may be in danger of contracting bronchiolitis obliterans. David Michaels, of the George Washington University School of Public Health, first published Rose's warning letter on his blog.[10][11][12]

On 4 September 2007, the Flavor and Extract Manufacturers recommended reduction of diacetyl in butter-like flavorings. The next day ConAgra Foods announced that it would soon remove diacetyl from its popcorn products.[15]

On 16 January 2008, it was announced that Wayne Watson, the Denver consumer who developed "popcorn lung" after inhaling microwaved popcorn, was suing the Kroger grocery store chain and its affiliates. In the lawsuit, filed in U.S. District Court, Watson's attorney claimed that the companies "failed to warn that preparing microwave popcorn in a microwave oven as intended and smelling the buttery aroma could expose the consumer to an inhalation hazard and a risk of lung injury."[16]

Diacetyl is approved by the Food and Drug Administration as a safe flavor ingredient, but there is evidence to suggest that inhalation in large amounts is dangerous. There are currently no warnings from federal regulators about diacetyl.


Bronchiolitis obliterans is often misdiagnosed as asthma, bronchitis, emphysema, or pneumonia.

Diagnosis may include the following tests:

  • Chest X-rays tests.
  • Diffusing capacity of the lung (DLCO) tests are usually normal.
  • Spirometry tests show fixed airway obstructions and sometimes restriction. FEV1/FVC may therefore be <75%.
  • Lung volume tests may show hyperinflation (excessive air in lungs caused by air trapping).
  • High-resolution computerized tomography scans of the chest at full inspiration and expiration may reveal heterogeneous air trapping on the expiratory view as well as haziness and thickened airway walls.
  • Lung biopsies may reveal evidence of constrictive bronchiolitis obliterans (i.e., severe narrowing or complete obstruction of the small airways). An open lung biopsy, such as by thoracoscopy, is more likely to be diagnostic than a transbronchial biopsy. Special processing, staining, and review of multiple tissue sections may be necessary for a diagnosis.[4]


This disease is irreversible and severe cases often require a lung transplant. Evaluation of interventions to prevent bronchiolitis obliterans relies on early detection of abnormal spirometry results or unusual decreases in repeated measurements.

See also


  1. ^ Brant & Helms (1999). Fundamentals of Diagnostic Radiology. Baltimore: Williams & Wilkins. ISBN 0683300938. 
  2. ^ Webb, et al. (2000). High Resolution CT of the Lung (3rd ed.). Philadelphia: Lippincott Williams & Wilkins. ISBN 0781702178. 
  3. ^ Center for Disease Control (2002). Fixed obstructive lung disease in workers at a microwave popcorn factory (7th ed.). 
  4. ^ National Institute for Occupational Safety and Health. Preventing lung disease in workers who make or use flavorings, 2004
  5. ^ Colby, T.V. "Bronchiolitis, Pathologic Considerations". Am J Clin Pathology 1998;109:101-9
  6. ^ National Institutes of Health. Haz-Map; Information on Hazardous Chemicals and Occupational Diseases by Jay A. Brown, M.D., M.P.H.
  7. ^ California Department of Public Health
  8. ^ E. Neil Schachter. "Popcorn Workers' Lung". New England Journal of Medicine 2002;347(5):360-1.
  9. ^ David Egilman (2007). "Popcorn Workers Lung"
  10. ^ "Doctor warns consumers of popcorn fumes", Marcus Kabel, Associated Press, September 5, 2007, hosted by Yahoo! News, retrieved 2007-09-10. (dead link)
  11. ^ Letter from Cecile Rose to U.S. Food and Drug Administration, from
  12. ^ David Michaels (2007). Popcorn Lung Coming to Your Kitchen? The FDA Doesn’t Want to Know, a blog post at
  13. ^ Reuters New Report: FDA to probe popcorn link in man's lung disease.
  14. ^ Weaver Popcorn Company Press Release: "Pop Weaver Introduces First Microwave Popcorn With Flavoring Containing No Diacetyl", 2007-08-27, hosted at "Pop Weaver introduces first microwave popcorn with flavoring containing no diacetyl"PDF (216 KiB).
  15. ^ USA Today. ConAgra to drop popcorn chemical linked to lung ailment
  16. ^ Man sues for "popcorn lung" by George Merritt, Associated Press Online edition, accessed Apr 29 2011.


  1. ^ Ezri, T.; Kunichezky, S.; Eliraz, A.; Soroker, D.; Halperin, D.; Schattner, A. (Jan 1994). "Bronchiolitis obliterans--current concepts". The Quarterly Journal of Medicine 87 (1): 1–10. PMID 8140211.  edit
  2. ^ Hayakawa, H.; Sato, A.; Imokawa, S.; Todate, A.; Chida, K.; Suzuki, K.; Iwata, M. (Jun 1998). "Diffuse panbronchiolitis and rheumatoid arthritis-associated bronchiolar disease: similarities and differences" (Free full text). Internal Medicine (Tokyo, Japan) 37 (6): 504–508. doi:10.2169/internalmedicine.37.504. ISSN 1349-7235. PMID 9678682.  edit
  3. ^ Schlesinger, C.; Meyer, C.; Veeraraghavan, S.; Koss, M. (Jan 1998). "Constrictive (obliterative) bronchiolitis: diagnosis, etiology, and a critical review of the literature". Annals of Diagnostic Pathology 2 (5): 321–334. doi:10.1016/S1092-9134(98)80026-9. PMID 9845757.  edit
  4. ^ Merriam-Webster Medical Dictionary > bronchiolitis obliterans Retrieved on August, 2010
  5. ^ "Dorlands Medical Dictionary:bronchiolitis fibrosa obliterans". Retrieved 2008-11-17. 
  6. ^
  7. ^ Harber P, Saechao K, Boomus C (2006). "Diacetyl-induced lung disease". Toxicol Rev 25 (4): 261–272. doi:10.2165/00139709-200625040-00006. PMID 17288497. 


  • Brant & Helms. Fundamentals of Diagnostic Radiology LWW, 1999.
  • Webb, et al. High Resolution CT of the Lung. 3rd edition. LWW, 2000.

External links

Wikimedia Foundation. 2010.

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