Pulmonary complications associated with HSCT

While outcomes for patients who undergo allogeneic hematopoietic stem cell transplantation (HSCT) have improved over the past 10-20 years, pulmonary complications after allogeneic HSCT remain a leading cause of morbidity and mortality. Overall, 25-50% of pediatric HSCT patients will develop pulmonary complications. Thus, prevention, early detection, and intervention are key to minimizing the sequelae from HSCT-associated pulmonary complications. HSCT-associated pulmonary complications can be classified as infectious or noninfectious, and they often follow a predictable timeline, occurring during discrete phases of HSCT (preengraftment, early post-engraftment, late post-engraftment). However, certain post-HSCT pulmonary complications span the entire post-HSCT course. The most common causes of noninfectious pulmonary complications are related to the conditioning regimen used which can result in varying degrees of acute or delayed lung injury, the degree of recipient-donor HLA histoincompatibility, the hematopoietic stem cell (HSC) source, the degree of graft manipulation, and the development of graft-versus-host disease (GvHD), both acute and chronic. Infectious etiologies can be caused by any class of pathogen including bacterial, viral, fungal, and protozoan. They usually occur during periods of profound and/or prolonged neutropenia and/or impaired or delayed cellular and humoral immune recovery. Immunosuppression used to prevent or treat GvHD also places a HSCT recipient at high risk for developing pulmonary infections that can be life-threatening. This chapter discusses the most common pulmonary complications associated with HSCT by time period post-HSCT.