Managing bronchiolitis obliterans syndrome (BOS) and chronic lung allograft dysfunction (CLAD) in children: what does the future hold?

The success of pediatric lung transplantation continues to be limited by long-term graft dysfunction. Historically this has been characterized as an obstructive spirometric defect in the form of the bronchiolitis obliterans syndrome (BOS). It is recognized, however, that this does not reflect many of the other acknowledged etiologies of chronic lung dysfunction-noting it is the sum of the parts that contribute to respiratory morbidity and mortality after transplant. The term chronic lung allograft dysfunction (CLAD) has been coined to reflect these other entities and, in particular, a group of relatively recently described lung disorders called the restrictive allograft syndrome (RAS). RAS is characterized by a restrictive spirometric defect. Although these entities have not yet been studied in a pediatric setting their association with poor compliance, antibody-mediated rejection (AMR), and post-infectious lung damage (particularly viral) warrants attention by pediatric lung transplant teams. Current therapy for the BOS subset of CLAD is otherwise limited to changing immunosuppressants and avoiding excessive infectious risk by avoiding over-immunosuppression. Long-term macrolide therapy in lung transplantation is not of proven efficacy. Reviewing previous BOS studies to explore restrictive spirometric cases and joint projects via groups like the International Pediatric Lung Transplant Collaborative will be the way forward to solve this pressing problem.