Chronic lung allograft dysfunction post-lung transplantation: The era of bronchiolitis obliterans syndrome and restrictive allograft syndrome

Table 1 Phenotypes of chronic lung allograft dysfunction

	Obstruction findings	Restriction findings	CT findings
	FEV1/FVC < 0.7	TLC decline ≥ 10% from baseline	Parenchymal opacities and/or pleural thickening
BOS	√
RAS		√	√
Mixed	√	√	√
Undefined (2 types)	√		√
	√	√

BOS: Bronchiolitis obliterans syndrome; CLAD: Chronic lung allograft dysfunction; CT: Computed tomography; FEV1: Forced expiratory volume in 1 second; FVC: Forced vital capacity; RAS: Restrictive allograft syndrome; TLC: Total lung capacity; √: Yes; Black box: No.

Table 2 Possible risk factors of bronchiolitis obliterans syndrome and restrictive allograft syndrome based on the clinical evidence

BOS	Undetermined[5,23]	RAS
Early-onset DAD[24]	ACR	AFOP[29]
	Air pollution[37]	AMR1[27]
	Aspiration/GERD	Elevated eosinophils in blood and BAL[25]
	CMV pneumonitis	HLA-DRB1/3/4/5 + DQA/B[28]
	Colonization of Pseudomonas aeruginosa and Aspergillus	Late-onset DAD[24]
	PGD	LB1[23]
		Specific recipients’ lung disease (COPD/ ILD/IPF)[26]

¹AMR and LB might be associated with the development of RAS compared with BOS. ACR: Acute cellular rejection; AFOP: Acute fibrinoid organizing pneumonia; AMR: Acute antibody-mediated rejection; BAL: Bronchoalveolar lavage; BOS: Bronchiolitis obliterans syndrome; COPD: Chronic obstructive pulmonary disease; CLAD: Chronic lung allograft dysfunction; CMV: Cytomegalovirus; GERD: Gastro esophageal reflux disease; LB: Lymphocytic bronchiolitis; RAS: Restrictive allograft syndrome.