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Updated: Jun 3, 2026
08:22
Orthotopic Left Lung Transplantation in Rats
Published on: July 3, 2025
Restrictive allograft syndrome (RAS): a novel form of chronic lung allograft dysfunction
Masaaki Sato1, Thomas K Waddell, Ute Wagnetz
1University Health Network, University of Toronto, Ontario, Canada.
Summary
Restrictive allograft syndrome (RAS) is a newly identified form of chronic lung allograft dysfunction (CLAD) following lung transplantation. This condition, characterized by lung fibrosis, significantly worsens patient survival compared to bronchiolitis obliterans syndrome (BOS).
Area of Science:
- Pulmonary Medicine
- Transplantation Immunology
- Radiology
Background:
- Chronic lung allograft dysfunction (CLAD) is a major complication after lung transplantation.
- Bronchiolitis obliterans syndrome (BOS) with obstructive physiology is the most recognized form of CLAD.
- A distinct CLAD phenotype with restrictive functional changes and peripheral lung pathology has been observed.
Purpose of the Study:
- To investigate the characteristics of a CLAD form involving restrictive functional changes and peripheral lung pathology.
- To define and identify this novel CLAD phenotype, termed Restrictive Allograft Syndrome (RAS).
- To compare the clinical features and survival outcomes of RAS with BOS.
Main Methods:
- Retrospective analysis of bilateral lung transplant recipients (1996-2009).
- Defined CLAD as FEV(1) < 80% of baseline.
- Defined RAS as CLAD with total lung capacity decline threshold at 90% baseline; BOS as CLAD without RAS.
- Utilized Cox proportional hazards models and Kaplan-Meier analyses for survival estimation.
Main Results:
- Out of 156 CLAD cases, 47 (30%) exhibited the RAS phenotype.
- RAS patients showed significant interstitial lung disease on CT scans (p < 0.0001) compared to BOS patients.
- RAS was associated with significantly worse patient survival post-CLAD onset (median 541 days vs. 1,421 days for BOS; p = 0.0003).
- RAS was the most significant risk factor for death after CLAD onset (HR, 1.60).
Conclusions:
- Restrictive Allograft Syndrome (RAS) represents a novel and distinct form of CLAD.
- RAS is characterized by peripheral lung fibrosis and significantly impacts lung transplant recipient survival.
- Identification and understanding of RAS are crucial for improving outcomes in lung transplant patients.
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