Post-Transplant Complications

Hematopoietic cell transplantation (HCT) is a potentially curative therapy for patients with high-risk malignant and nonmalignant conditions. Nevertheless, various post-allogeneic HCT (allo-HCT) complications with diverse chronology, etiology, and pathophysiological background can develop, including general and organ-specific complications, such as graft dysfunction, infectious, and non-infectious etiologies, as well as non-infectious pulmonary complications (NIPCs). Post-transplant complications can also be related to conditioning intensity and drug-specific side effects. However, treatment options for these complications are suboptimal at present. Poor graft function (PGF) is a potentially life-threatening post-allo-HCT complication and is reported in 5-30% of patients. Nevertheless, consensus guidelines to define and treat PGF are not available. Most therapies are symptomatic with variable success rates. NIPCs are diverse and difficult to diagnose. The pathophysiology of NIPCs remains ill-defined, and effective treatment approaches have not been standardized, with mortality exceeding 50% for some conditions, such as idiopathic pneumonia syndrome (IPS). Modification of the conditioning regimen intensity and introduction of novel agents have been used to decrease post-allo-HCT complications, including infections, non-infectious complications, graft-versus-host disease (GvHD), as well as cardiopulmonary, neurological, hepatorenal, and other complications. Transplant-associated thrombotic microangiopathy (TA-TMA) is a lethal post-allo-HCT complication that may be associated with functional and genetic abnormalities in complement activation and related to the use of calcineurin inhibitors, such as cyclosporine and tacrolimus. The introduction of complement inhibitors has transformed TA-TMA from a lethal complication to a treatable syndrome.