Disease Directory Bronchiolitis Obliterans Syndrome
Respiratory

Bronchiolitis Obliterans Syndrome

Also known as: BOS, constrictive bronchiolitis, post-transplant BO

Prevalence

Affects approximately 50% of lung transplant recipients by 5 years post-transplant

Onset

Post-transplant or post-injury (any age)

Type

Rare obstructive lung disease / allograft dysfunction

About Bronchiolitis Obliterans Syndrome

Bronchiolitis obliterans syndrome is a progressive fibro-obliterative disorder of the small airways that represents the major form of chronic lung allograft dysfunction following lung or haematopoietic stem cell transplantation. It is characterised by concentric fibrosis of bronchiolar walls leading to airflow obstruction that is not fully reversible with bronchodilators. Non-transplant causes include toxic fume inhalation, connective tissue disease, and autoimmune conditions, but the post-transplant form is most prevalent and studied.

Common Clinical Features

Progressive airflow obstruction (declining FEV1) Dyspnoea on exertion Dry cough Reduced exercise tolerance Recurrent respiratory infections Air trapping on CT imaging Absence of acute rejection features

Clinical Trial Eligibility Tips

What to know before applying to Bronchiolitis Obliterans Syndrome trials.

BOS is staged by percentage decline in FEV1 from post-transplant baseline (BOS 0-3); confirm your current BOS stage as trials often specify eligible stages.

Active acute rejection or concurrent infection usually disqualifies patients; ensure these are resolved and documented before applying.

Time since transplant and immunosuppression regimen are common eligibility variables; have your transplant centre provide a detailed medication history.

Patient Resources

Patient Organization

Lung Transplant Foundation

Visit website ↗

Orphanet

European reference resource for rare diseases (ORPHA:1303)

View on Orphanet ↗

NORD

National Organization for Rare Disorders

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Find recruiting Bronchiolitis Obliterans Syndrome trials

Search 500,000+ studies from ClinicalTrials.gov, filtered for Bronchiolitis Obliterans Syndrome. Updated daily.

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