Bronchiolitis obliterans syndrome

Bronchiolitis obliterans syndrome (BOS) is thought to represent chronic allograft rejection. Primary graft dysfunction (PGD), acute cellular rejection (AR), lymphocytic bronchiolitis (LB), abnormal gastroesophageal reflux (GER) with microaspiration, and allograft infection have all been implicated as causes of BOS. Although BOS is generally considered to be caused by alloimmune responses to non-self tissue, more recent findings suggest that autoimmune responses to self-antigens and the triggering of innate immune responses to environment stimuli may play a significant role in the pathobiology of BOS. Effective treatment of BOS remains elusive, but azithromycin may stabilize and possibly improve FEV1 in patients who meet criteria for BOS, and gastric fundoplication may be beneficial if abnormal GER is detected. Augmented immunosuppression is generally ineffective, and other treatments such as total lymphoid irradiation (TLI) or extracorporeal photopheresis (ECP) may not have a significant impact on loss of function. Retransplantation can be considered in carefully selected patients.