This study investigates the impact of letermovir prophylaxis on viral infections (including CMV, EBV, BKV, HHV-6/7, RSV, ADV, HSV, etc.) following allogeneic hematopoietic stem cell transplantation in pediatric patients with EBV-associated T/NK-cell lymphoproliferative diseases and refractory/relapsed EBV-related hemophagocytic lymphohistiocytosis. Additionally, we examine its effects on other transplantation complications, including engraftment failure, graft-versus-host disease (GvHD), disease relapse, thrombotic microangiopathy (TMA), overall survival (OS), post-transplant lymphoproliferative disorder (PTLD) incidence, and immune reconstitution.
Diagnosed with EBV-positive T/NK lymphoproliferative disease (EBV-T/NK LPD) according to ICC 2022 criteria, or diagnosed with refractory/relapsed EBV-associated hemophagocytic lymphohistiocytosis (EBV-HLH) according to the 2004-HLH diagnostic criteria;
Undergoing first allogeneic hematopoietic stem cell transplantation (allo-HSCT) at the study center;
Age < 18 years;
CMV seropositive (IgG+) prior to transplantation;
History of CMV end-organ disease within 6 months prior to enrollment;
Severe hepatic dysfunction (defined as Child-Pugh Class C);
End-stage renal impairment with creatinine clearance < 10 mL/min (calculated by Cockcroft-Gault equation);
Prior allogeneic hematopoietic stem cell transplantation;