Management of cytomegalovirus (CMV) reactivation is a crucial challenge following allogeneic hematopoietic cell transplantation (allo-HCT). The goal is to control CMV reactivation before it progresses to CMV-related diseases. There are several risk factors for CMV reactivation which can be categorized into patient-related, donor-related, transplantation method-related factors, and post-transplantation events. Currently, the most common approach to CMV reactivation involves a prophylactic strategy by letermovir or a presumptive treatment by monitoring the CMV viral load.

 CMV reactivation is generally considered to be an independent risk factor for non-relapse mortality and other complications, and several issues remain a matter of debate, including the clinical relationship between CMV and graft-versus-host disease, and the impact of CMV reactivation on leukemia relapse or opportunistic infections. Furthermore, for long-term control of CMV infection post-transplantation, it is essential to rely not only on drug treatments but also on immune control. This review article will present several recent findings regarding CMV immunity after allo-HCT. The fact that many allo-HCT recipients still suffer from CMV reactivation or CMV-related diseases indicates that numerous challenges still need to be addressed. Therefore, it is expected that a more comprehensive strategy against CMV will arise from various perspectives in the future.

 The impact of HLA matching of patient and donor in allogeneic hematopoietic stem cell transplantation (allo-HSCT) has been analyzed mainly in unrelated hematopoietic stem cell transplantation (UR-HSCT), where large-scale clinical and HLA database are available. Next-generation sequencing based HLA typing have made it possible to detect polymorphisms in the entire HLA gene, and it have provided new insights into the significance of HLA in allo-HSCT. Dimoriphism at -21 of HLA-B exon 1 gives rise to leader peptides with either methionine or threonine at the second position of the leader. Dimorphic HLA-B leader has been demonstrated to be useful for predicting the risk of graft-versus-host disease (GVHD). It has been shown that differences in HLA-DQ heterodimers formed by HLA-DQA1 and-DQB1 gene products may differently affect transplant outcomes. Although allo-HSCT with alternative donors such as HLA haploidentical related donor and unrelated cord blood has become widely performed, the impact of HLA incompatibility on transplant outcomes has been shown to vary depending on the stem cell source. This review outlines our emerging understanding of the impact of HLA on allo-HSCT for optimal donor selection.

 Hepatic sinusoidal obstruction syndrome/veno-occlusive disease (SOS/VOD) is a well-known liver complication following hematopoietic stem cell transplantation. To diagnose SOS/VOD, it is often difficult to perform percutaneous liver biopsy because of the bleeding tendency. Therefore, several clinical diagnostic criteria (Seattle, Baltimore, and EBMT) have been proposed. Defibrotide, as the only approved agent, should be administered early (within two days of SOS/VOD diagnosis). It is important to make the early diagnosis of SOS/VOD. Recently, the refined EBMT 2023 criteria were introduced, and HokUS-10 has attracted worldwide attention as an ultrasound diagnostic tool.

 Clinically, it is crucial to “suspect and diagnose SOS/VOD early and start defibrotide treatment early” and collaborate with medical staffs, including sonographers to save patients with SOS/VOD.