A new classification system for chronic lung allograft dysfunction

J Heart Lung Transplant. 2014 Feb;33(2):127-33. doi: 10.1016/j.healun.2013.10.022. Epub 2013 Oct 24.


Although survival after lung transplantation has improved significantly during the last decade, chronic rejection is thought to be the major cause of late mortality. The physiologic hallmark of chronic rejection has been a persistent fall in forced expiratory volume in 1 second associated with an obstructive ventilatory defect, for which the term bronchiolitis obliterans syndrome (BOS) was defined to allow a uniformity of description and grading of severity throughout the world. Although BOS was generally thought to be irreversible, recent evidence suggests that some patients with BOS may respond to azithromycin with > 10% improvement in their forced expiratory volume in 1 second. In addition, a restrictive form of chronic rejection has recently been described that does not fit the strict definition of BOS as an obstructive defect. Hence, the term chronic lung allograft dysfunction (CLAD) has been introduced to cover all forms of graft dysfunction, but CLAD has yet to be defined. We propose a definition of CLAD and a flow chart that may facilitate recognition of the different phenotypes of CLAD that can complicate the clinical course of lung transplant recipients.

Keywords: ARAD; BOS; CLAD; Lung transplantation; RAS; classification system.

Publication types

  • Editorial

MeSH terms

  • Allografts
  • Azithromycin / therapeutic use
  • Bronchiolitis Obliterans / drug therapy
  • Bronchiolitis Obliterans / physiopathology
  • Chronic Disease
  • Forced Expiratory Volume / physiology
  • Graft Rejection / classification*
  • Graft Rejection / physiopathology
  • Humans
  • Lung / physiopathology*
  • Lung Transplantation*
  • Phenotype*
  • Terminology as Topic*


  • Azithromycin