**2.2. PTLD in HSCT**

PTLD develops in approximately 1% of patients post HSCT, among which the majority of cases occur within the first year after allogeneic stem cell transplantation (alloSCT). It is highly related to EBV reactivation. Risk factors that associate with high incidence of EBVrelated PTLD include elderly patients (aged ≥50 years at transplantation), T-cell depletioncontaining regimens, antithymocyte globulin (ATG) use, and grafts derived from unrelated or HLA-mismatched donors. PTLD can also develop in patients who received autologous stem cell transplants, but the frequency is much lower than alloSCT [9, 10]. PTLD in ASCT cases occurs in younger age group, with shorter duration of onset than solid organ transplantation.
